1200-Baud Archeology

jamie found this singularly geeky article on reconstructing Apple I BASIC from a cassette tape. It claims to offer the first confirmed perfect dump (BIN) of the 4096 bytes of this venerable interpreter. Terrific fun for the whole family. "The Apple I is extremely rare. Only 200 were built, and less than 100 are believed to be in existence. Neither Steve nor Woz own an Apple I any more, and neither does Apple Inc. The cassettes are even rarer, as not every Apple I came with one... So here is how to decode the signal. Let us first open the audio file in Audacity and look at the waveform... It is now time to write a small program to measure and dump the width of the pulses."

Comments

Alternative tools

[stryyker]

Probably would have been useful for the person to look at how C64 emulators and people handle transfer C64 tapes to PC.

Re:Alternative tools

[Alioth]

Yes - I thought this too - the article's slashdotted at the moment but the summary makes me think he made a mountain from a molehill. In the Sinclair Spectrum world, loading Speccy tapes on to a PC, and encoding them in a useful format (TZX) has been a solved problem for years.

All these tape formats were physically pretty similar when it comes to how they were encoded, and the same techniques could have been used by looking at any home computer emulator that loaded stuff from tape even if the details were different.

Re:Alternative tools

[KGIII]

I was actually thinking VIC 20. (I painfully admit that the first was not a woman but a PET and my father and I built a wooden case for it but that predated the VIC 20 by about a year or so.) I played FLOG off of tape and saved my SkiDownHillFaster game to tape damn it! Now somoene better get off my lawn but probably not you.

Re:Alternative tools

[lpontiac]

the summary makes me think he made a mountain from a molehill.

I think the emphasis is more on the historical significance, given the rarity of the tapes and the fact that the only digitised copy floating about has been patched.

Re:Alternative tools

[CharlieG]

Actually, If I remember right (digging back oh, nearly 30 years into the recesses of my mind), the C-64 had a fairly unusual tape format, unlike almost everyone else, just like their disk drive was unique (everyone else used a fixed number of sectors/track, where Commodore used a variable number, with more sectors/track as you moved out, to get more data on the disk)

Re:Alternative tools

[Dan East]

The article comes up fine for me. He lists a simple C routine comprised of 15 or so lines of code. So it wasn't like he made that big of a mountain out of it.

Re:Alternative tools

[Lumpy]

Didn't the Apple I use PSK instead of FSK encoding for the tape audio?

I though instead of Shifting frequency they shifted phase which is quite a but harder to detect than frequency shift.

BTW: Computer Tapes worked great to load software across Ham radio. 2 meter radio, I would load a game from a friend across the city over 2 meters by simply patching audio from the rig to the computer.

Luckily the C64 had a very slow bitrate (even the floppy drive was slow as hell) for it's storage tapes so it worked great.

Re:Alternative tools

[YeeHaW_Jelte]

The code being simple does not necessarily mean the though process of coming to those 15 lines was simple and/or straightforward.

Re:Alternative tools

[badran]

So you had better wifi then....

Re:Alternative tools

[daBass]

There used to be a Dutch radio program in the 80s called "NOS Hobbyscoop" that had their own basic interpreter for many computers of the day. (MSX, Acorn, Sharp MZ, etc.)

They actually broadcast computer programs every week on medium wave AM. They'd count down, you start the cassette recorder and you had some new programs.

Fun for the whole family, even if a bit painful on the ears!

Re:Alternative tools

[Miamicanes]

Has anyone written a program that can take a .wav sample of a poor-quality c64/vic 20 tape (stretched tape, warbling output, drifting volume level, etc) and do modern DSP analysis on it to turn it into something the more mundane .wav->.tap converters can handle? I unfortunately don't have the background to actually implement such a beast, but from what I know about both DSP and the way signals were recorded to tape by a Datasette/C2N, it *should* be a somewhat straightforward exercise. In theory, it might even be possible for a software DSP to recognize "print through" artifacts and accommodate for them.

Going a step further, does there exist a guide to the tokenization scheme used by BASIC on the Vic/64, so if there end up being a couple of mangled/indeterminate bytes, the proper values can be guessed based upon their context and the values of the surrounding bytes (assuming it's not in the middle of something mostly context-free, like a DATA statement)?

I have a couple of Vic-20 programs I wrote back in middle school that I'd love to recover for nostalgia reasons, but I've never been able to get any of the .wav conversion software to take them because the average volume level's drift tends to exceed the high/low threshold. In other words, I can only get a semi-intact CRC-error-free dump of the header and first few bytes if I set the threshold to something like 1 or 2, but within a second or two of the main recording starting, its average volume level drifts up or down enough to put "low" above the beginning's "high" threshold, or "high" below the beginning's "low" threshold. And most of the programs I've seen aren't much more sophisticated than the C64/Vic 20's own tapeloading routines were. For example, they might use the two copies to determine an error, but they don't even try to use the good parts of both copies to produce a single error-free result. The original hardware/software didn't do it because there wasn't enough RAM... but modern software has no such limit ;-)

Re:Alternative tools

[Mr Z]

No. It's FSK, but it used a constant number of zero crossings per bit, rather than a constant bit period. So, to decode it, you count the average time between zero crossings rather than the number of zero crossings in a fixed time window.

On the plus side, it seems like the Woz scheme has some benefits. If you assign the shorter bit period to the more common bit value (likely, '0'), you shorten your average recording length a little. On the minus side, if you get an extra zero crossing in there (say, due to noise that wasn't filtered away by a Schmitt trigger or other hysteresis somewhere), recovery may be awkward.

BTW, the C64 floppy drives were slow as heck, but that had nothing to do with the bitrate for its media. There's some goofy history there, involving bugs in the shift register on the VIC-20's PIA, the decision to use CPU control loops instead to determine the bit period when communicating between the drive and the machine, and then the greater cycle-stealing period of the VIC-II as you get to the C64 throwing a monkey wrench in the works. The fast-load carts worked by restoring the native CIA hardware shift register to get rid of the CPU-controlled bit shifting to read bits from the floppy, restoring its speed to performance levels similar to the old IEEE-488 based bus they used back in the Commodore PET era. But that's a different story for another day.

--Joe

Re:Alternative tools

[linhux]

When I was a teenager, I used to decode FAT tables and directory structures by hand, using pen and paper and printouts from a raw hex dump of a hard disk. I didn't do this because there was a problem needed to be solved; I knew what was on the disk and there sure were plenty of tools to read the data (like MS-DOS). But it was a fun challenge and I learned how FAT worked.

I can see how this is a similar challenge. It's nothing more than a geeky sudoku.

Re:Alternative tools

[Anonymous Coward]

No. It's FSK, but it used a constant number of zero crossings per bit, rather than a constant bit period. So, to decode it, you count the average time between zero crossings rather than the number of zero crossings in a fixed time window.

Um, that's PSK.

Re:Alternative tools

[Temkin]

You forgot that there were more signal lines available, but unused. They had serial in and serial out. The fastload cartridges turned one line around and implemented a 2-bit parallel transfer. Fastload carts also offered a great place to solder in a reset button.

I'd tell you to get of my lawn, but that would just make more rocking chair ruts...

Re:Alternative tools

[Mr Z]

No. PSK is a constant carrier frequency with shifts in phase. PSK still uses constant bit periods. Apple's format uses two different frequencies, with a constant number of cycles per bit.

Re:Alternative tools

[Creepy]

I have no idea how they formatted it, but it worked in any cassette player that had a line out (and a counter if you wanted to load any other program on the same tape). The Apple tape drive was no speedster either, although the one I was familiar with came with the 48k Apple ][ (with DOS 3.1 it took about 15 minutes to load - if you were lucky - sometimes it took 2-3 tries). My experience with the tape drive was short lived, however, as my school got Disk ][s that school year and we immediately switched (I remember begging my parents to buy me a single 5 1/4 inch floppy disk - I imagine they were expensive back then). Everyone I knew with Vic 20s and C64 had the abysmally slow tape drives (10-40 minutes to load anything). I didn't even see the C64 disk drive until the early 1990s and I agree, it was pitifully slow in comparison to the older Disk ][.

    What really got me hooked on the ][ was the release of Sabotage and Sneakers in 1981. Up until then I had only really played games on the Atari 2600 and Sears Super Video Arcade (a rebranded Intellivision), so it was eye opening that I could actually write the games I loved - by the time I was 12 I was writing Apple ][ assembler, which is kind of frightening to me in retrospect (I dodge assembly like the plague these days).

Re:Alternative tools

[C0vardeAn0nim0]

here in brasil, UFRGS (federeal university of rio grande do sul) broadcasted test programs using stereo FM. one chanel would broadcast audio, the other encoded text to be decoded by an MSX computer and displayed on screen. the idea was to make talk radio accessible to def people.

Re:Alternative tools

[Alioth]

That's also how the Spectrum loading scheme worked, too. A zero took less time than a 1. As a consequence there wasn't a fixed baud rate, but the average speed with the Spectrum's scheme was 1500 bps. Custom schemes were also made too, but they were all generally the same 'constant number of zero crossings per bit', but at different frequencies (generally for higher loading speed, or to make tape copying less trivial). Some people even used Manchester encoding (which was faster for the same fundamental frequency). I've toyed with the idea of making an NRZI tape save/load routine using 4B5B coding, since it should work and no one did it (at least on the Spectrum!)

Re:Alternative tools

[Mr Z]

The 2-bit thing is still a hack that only buys back some of the performance. The original intention was to use the VIA's (I mistakenly called it the PIA) shift register, which would have kept it fast. For those of you who really care, someone actually wrote this all up on Wikipedia.

And you're right, I was thinking of a different loader that uses the synchronous serial mode, and that requires a hardware mod. *sigh* I never owned a C64 back in the day (though I have one now), so I only got to hear about all these hacks.

I get off your lawn if you get off mine. ;-)

Re:Alternative tools

[Mr Z]

Probably the most elaborate scheme I've seen so far is the Mattel Electronics Keyboard Component. It encodes everything into blocks of 32 10-bit words, each protected by a 5-bit detect-2-correct-1 Hamming code. The 32 words are then re-interleaved as 15 32-bit words. Each 32-bit word gets prefixed with a 5-bit framing header. That's prefixed by a block of zeros and a special 64-bit sync pattern per block. (I believe the whole sync structure was about 256 bits long.) The whole shebang is then Manchester encoded and put out to tape. Furthermore, the drive had a carrier-detect signal that it supplied in addition to the Manchester decoded bits.

The net result is a fairly robust protocol. Because the 32 data words were interleaved, dropout errors would get spread among multiple words. Thus, a burst error would show up only as 1 or 2 bit errors in each individual word. In addition, if a given word shows up as non-correctable, it was sometimes recoverable by flipping bits based on where the carrier was lost and trying again.

Other nifty aspects of its design: There was an additional pre-header on blocks that was recorded at (I think) 1/3rd the normal carrier frequency. This allowed the drive to detect interesting headers while fast-forwarding or rewinding. Since the drive was computer controlled, it allowed for fully automatic operation, including hardware seeks.

What was the bit rate? Well, I believe the raw bit rate for data bits coming off the tape was about 3000 bps. Factoring in encoding overhead, though, I'd say the final throughput was less than half that. A quick calculation suggests a nominal throughput around 1200 baud, give or take.

--Joe

Re:Alternative tools

[Mr Z]

Just a quick followup: By 3000bps, I'm referring to the Manchester decoded bits. As I recall, the hardware actually did the Manchester decode, and then interrupted the CPU with every new bit. Good thing the Keyboard Component was a dual-CPU system. :-)

Re:Alternative tools

[jez9999]

Sorry to OT the thread with this and I guess I'll get modded down, but it's taken me this long to figure out that Slashdot doesn't have an internal messaging system (Why the hell not? E-mail sucks now, not good enough.)

Anyway,

Oolite: Elite-like game. For Mac, Linux and Windows [aegidian.org]

Alioth, what do you think is the best ever Elite game or Elite clone ever made? Is it Oolite, or is there something better about the retro NES version?

Re:Alternative tools

[Tumbleweed]

There used to be a Dutch radio program in the 80s called "NOS Hobbyscoop" that had their own basic interpreter for many computers of the day. (MSX, Acorn, Sharp MZ, etc.)

They actually broadcast computer programs every week on medium wave AM. They'd count down, you start the cassette recorder and you had some new programs.

Very interesting - that may be the first instance of P2P!

Re:Alternative tools

[A440Hz]

Perhaps, after he decoded the digitised data, he accidentally crashed his red-coloured lorry into the rear garden?

Re:Alternative tools

[HTH NE1]

What really got me hooked on the ][ was the release of Sabotage and Sneakers in 1981.

Heh, I liked SABOTAGE so much I first repackaged it as a SYS file to run it under ProDOS, then a full disassembly of it, which led to removal the last bit of copy protection in it (intended to prevent memory dump cards, it would periodically test the data in the second text screen's screen holes and go into a memory-wiping loop, which also prevented going into the Apple IIgs Control Panel to adjust the processor speed).

I had intended eventually to upgrade the game to use Apple IIgs graphics, a saved high score list, and include day, night, and weather cycles. Unfortunately, even with a complete disassembly of the code, a lookup table for the new screen memory and new raster sprites, I never got myself a real assembler to make the final product (the new sprites required more memory than the original, so memory would have to shift to accommodate them).

If anyone knows of a free cross-assembler for Mac OS X to compile 65c02/65c816 assembly source, I'll dig out my old disks.

Re:Alternative tools

[Detritus]

That's quite impressive for the time. I wonder if it was designed by an engineer or programmer who was moonlighting from a job at JPL.

Re:Alternative tools

[Detritus]

I've done work on recovering data from old analog tapes. You could clean up the signal by running it through a DC-blocking filter, which is a high-pass filter with a very low cut-off, and a software AGC with a short time-constant. Some of the noise can be eliminated with a low-pass filter. There isn't much that can done to eliminate speed variations. The best thing that you can do is to write a demodulator routine that can track the speed variations and has generous allowances for timing errors in the signal. Looking for zero crossings works OK on relatively clean signals. For more challenging material, you want to integrate over the time period of each bit.

Re:Alternative tools

[Mr Z]

It was put together by a handful of bright folks working for APh Consulting out of Cal-Tech, actually. I've actually met one of the two people involved in that project.

Re:Alternative tools

[Anonymous Coward]

I used nibble around on my C64, mostly because I was curious what there was to find on the disk. It also was a fun way to learn cheats for games.

Re:Alternative tools

[XHIIHIIHX]

FastLoad you Maverick

Re:Alternative tools

[Mr Z]

I'd like to post a minor correction in case someone comes along and notices the above description. I wrote the above from memory, and later realized I goofed on a couple details.

The lead-in to a block of data is a minimum of 256 zeros, followed by 4 32-bit words that have '1s' at the end in a special pattern that forms a "countdown until live". So, the header is a bit longer than I stated.

On the flip side, the total recorded block can have multiple sub-blocks associated with it, so the cost of that lead-in is amortized over a longer space. So, each 15x37 sub-block (555 bits) contains 32x10 = 320 useful bits. That's not so bad an overhead, really. Therefore, the peak bit rate is closer to 1700 bps.

Adding to the sophistication, the cassette drive has a 4-track head. The four tracks are divided up as follows:

• Prerecorded data
• Prerecorded audio
• Writable data
• Writable audio

The unit used specially formatted data tracks to time animations with respect to the audio, using a system called PicSe (pronounced "pixie"). You could store your own data on the data track, and in programs such as French Language cassette, you could store your own speech to compare against the pre-recorded model speech. Like I said, a very sophisticated system.

Re:Alternative tools

[Anonymous Coward]

I was permanently scarred by my otherwise much-loved Exidy Sorcerer's tape I/O in the early 80s. I never used one again (except for DAT backup).

The Australian Sorcerer had a kludged 240V power supply which dumped lots of heat. Guess what circuitry was right next door?

The heat would change the characteristics of the circuit such that it refused to read tapes after a while, and you could never rely on saving once. You had to save two or three times in the hope that one had worked. You tried "cold" and "hot" saves when possible. Of course the only way to tell if it worked was to load it over what you were trying to save. I dread to think how reliable some of these tapes might be after thirty years.

I bought a disc drive with my next machine.

Re:Alternative tools

[Alioth]

Probably Elite (disc version) for the BBC Micro. It certainly had the best sounds. I never played ArcElite, but those who did think it's the best, and some of the fundamental features of Oolite are inspired by ArcElite.

this makes me want to take a dump of my own

[Anonymous Coward]

*off to bathroom*

I'll report my findings later

Re:this makes me want to take a dump of my own

[Anonymous Coward]

be sure to check the logs

Re:this makes me want to take a dump of my own

[eclectro]

be sure to check the logs

There are no logs with a cload.

Re:this makes me want to take a dump of my own

[morgan_greywolf]

Mod parent Informative!

Re:this makes me want to take a dump of my own

[74nova]

mod parent "whoosh"!

Re:this makes me want to take a dump of my own

[Tiro]

Funny, I thought they were called core dumps.

Re:this makes me want to take a dump of my own

[Ant P.]

Is that +1 Informative or -1 TMI?

Sounds like a great idea for an iPhone app.

[jcr]

It would be way cool to have an Apple I emulator on my phone. Come to think of it, a DEC PDP-1 emulator with SpaceWar would be pretty sweet, too.

-jcr

Re:Sounds like a great idea for an iPhone app.

[funaho]

Hmm I wonder if I could port XGS to my Treo? :)

Re:Sounds like a great idea for an iPhone app.

[operagost]

This might work on an iPhone. It is actually running on a PDP-1 emulator.

Re:Sounds like a great idea for an iPhone app.

[ch-chuck]

Why not - I have an Atari 800 emulator running on my old iPaq ARM based pda. Games requiring a twitchy joystick are hard to play but some like chess, Temple of Apshai and Kennedy Approach are a lot of fun.

Re:Sounds like a great idea for an iPhone app.

[Anonymous Coward]

And check out what gamingmuseum is running on!

Apache/2.0.52 (OpenVMS) DAV/2 PHP/4.3.10 mod_perl/1.999.21 Perl/v5.8.6

Re:Sounds like a great idea for an iPhone app.

[mattack2]

It's not for your phone, but you do know about the Replica I board, right?

http://www.applefritter.com/briel

Re:Sounds like a great idea for an iPhone app.

[fermion]

I am amazed at what people are paying $7.99+ on iTunes. However, if Trade Wars became an iPhone App, then perhaps that would be one game that is worth the money.

Re:Sounds like a great idea for an iPhone app.

[jcr]

No, I hadn't heard about that. I'd love to get one of those when I have the time to bring it up.

-jcr

Doing it the hard way

[MichaelSmith]

It is now time to write a small program to measure and dump the width of the pulses

Its just an FSK modem. I have an old computer right here in my house which would demodulate that, once I bumped the clock rate up by a factor of four.

Re:Doing it the hard way

[Hal_Porter]

Yes. But a few people did some very magical things with tapes before the became obsolete. I saw a demo of a turbo tape system on an Atari 800XL which could load games "faster than a disk drive". Actually it about tied, but that was still impressive. The disk drive could probably managed 9600 baud sustained.

The modulator / demodulator was lump of potted electronics I could easily fit in my hand. Potting compound was a blank gunk you applied to electronics you didn't want people to tamper with, in this case to stop people seeing the components used. But whatever they were they could modulate and demodulate data at around 9600 baud. This was in the 80's back before DSPs too, so whatever circuit was used must have been made of Op Amps, transistors and passive components.

I never worked out how it worked. Though I can imagine exploiting the stereo nature of the tapes to send one carrier and phase shifted signal might work. Phase modulation is easy and demodulation is too if you have the carrier. Still phase modulation at 9kbaud+ would be a tight fit on an audio tape. I don't think things like QAM would be possible given the size of the package, the selling price (about twenty English pounds, or $40), and the primitive nature of 80's technology.

Re:Doing it the hard way

[MichaelSmith]

My 6502 system accessed the tape at 300 baud. I used an old cassette recorder for the job. I had my eyes on my uncles reel to reel hi-fi system. I reckon I could have got 9600 baud out of that just by exploiting the frequency response.

Re:Doing it the hard way

[Anonymous Coward]

The computer I designed and built around 1981 did 9600 bps with some TTL logic i designed myself. The format used was Manchester II, very simple to encode and decode if the clock can be recovered (the difficult part) for the decode phase. I think I used less PCB space than what was needed for the common 300 bps Kansas City format.

Re:Doing it the hard way

[Angstroem]

The hardware itself probably isn't much more than a compander and signal cleaner, e.g. some LM111 plus according resistors/capacitors like I used on my ZX81 to get 2k4 and 3k6.

To go into the 9k6 range, you could eventually go for 4 different frequencies marking 00, 01, 10, and 11 instead of just mark and space. A slightly more dedicated hardware therefore would also install 1 LP (00), 1 HP (11), and 2 BP (01, 10) filters to avoid any confusion.

I wonder if DTMF was ever used for data recording, giving you 16 different symbols and a nice analog way to separate the individual frequency components, therefore being easily able to reconstruct the 16 symbols.

Re:Doing it the hard way

[Hal_Porter]

The computer I designed and built around 1981 did 9600 bps with some TTL logic i designed myself. The format used was Manchester II, very simple to encode and decode if the clock can be recovered (the difficult part) for the decode phase. I think I used less PCB space than what was needed for the common 300 bps Kansas City format.

When the Atari sent data to the tape it had an internal modulator. But IIRC the demodulator was in the tape deck. And in any case you could output data to the disk drive, when it was a selectable baud 0-19200 rate and not modulated. So it seems like the turbo tape interface could use custom software to get 9600 baud TTL data to or from the tape and do its 9600 modem baud magic internally with a handful of components.

Tapes are stereo, so you could send the clock one one channel and the phase shifted clock (the signal) on the other.

You need an oscillator and a phase shifter made out of an XOR gate to modulate. Shifted single goes on one channel say left, unshifted one on the other, say right

To demodulate you use a phase detector made out of an XOR gate to compare the phase of the two channels.

This would be analogous to Manchester BPSK coding, except that you use one of the two audio channels to store the carrier so you don't need to spend expensive electronics regenerating it.

So something like this seems plausible. Unfortunately I didn't know enough about electronics back in the Atari days to try it.

Re:Doing it the hard way

[Lumpy]

That black potting compound was easy to defeat. I did it weekly back then yanking proms off of Digicipher boards for Satellite receivers.

Re:Doing it the hard way

[v1]

Potting compound was a blank gunk you applied to electronics you didn't want people to tamper with

They weren't so much worried about tampering as they were about reverse-engineering. Nowadays they have a different process they use on chips for cable boxes, which we saw an article here awhile ago on.

Re:Doing it the hard way

[repvik]

echo -e 'global _start \n _start: \n mov eax, 2 \n int 80h \n jmp _start' > a.asm; nasm a.asm -f elf; ld a.o -o a;

Too long for the signature field? It appears it would compile the forkbomb, but not run it. Or am I missing something? :)

Re:Doing it the hard way

[Anonymous Coward]

run the executable ( ./a )

Re:Doing it the hard way

[mikael]

The Atari 400/800/1200(XL) computers had stereo track tape recorders. The first track was used for saving/loading binary data. The second track was used for playing background music while loading. In theory it might have been possible for someone to build some electronics to convert the background music track for use as binary data as well, and thus booost the save/load speed.

Apple I BASIC?

[baldass_newbie]

Isn't that the buggy version that Woz built (and hated?)

Re:Apple I BASIC?

[Zaatxe]

Isn't that the buggy version that Woz built (and hated?)

Who cares? The fun is in recovering it, not using it! I'm sure that the archeologists that find mummies don't want to mummify dead people, they just want to learn about how the ancient people lived.

Re:Apple I BASIC?

[sootman]

If you can read Portuguese, check my blog

If you can use Babelfish, check out his blog :-)

Re:Apple I BASIC?

[Stormwatch]

That won't work, as that blog is a compilation of dumb, poorly written comments from a news site. An automatic translator won't get the typos. But if you can read Portuguese, it is really funny!

Re:Apple I BASIC?

[Zaatxe]

The automatic translator can add another layer of fun. For example, it translated my "caros leitores" to "expensive readers" instead of "dear readers"! Hehehe...

Re:Apple I BASIC?

[Anonymous Coward]

I wouldn't be too sure. Do you know many archaeologists?

Re:Apple I BASIC?

[Kj0n]

The fun is in recovering it, not using it!

The real fun is in irritating Woz by reporting all the bugs to him again.

Hey Woz. I just found this small program you wrote and boy, is this code terrible!

Re:Apple I BASIC?

[Mike610544]

From babelfish:

lately he is well difficult to obtain spoon pearls of the G1.

Indeed ...

I see this I eat a guarded form of censorship,

Whatever the original said, I'm thinking the translation is better.

Teach it!

[VincenzoRomano]

I think that at least the basic interpreter should be taught to the new generations.
They don't feel confortable enough in less than 1 GB, what if they had just 4 KB?

Re:Teach it!

[Technician]

I think that at least the basic interpreter should be taught to the new generations.

To rain on the parade, I wonder if there is a copyright violation in posting the code online un-edited. How long is copyright nowdays?

It's something we need to address in this age of IP property where the market has expired years ago but the copyright is in force for many more decades.

Re:Teach it!

[Digital Vomit]

How long is copyright nowdays?

Functionally "forever".

Re:Teach it!

[howardd21]

Really? I am not sure about that, it would effectively be telling them to to not use what was available to them. Should we also deny access to color? I understand the need to write tight code, but not sure putting the equivalent of shackles on a sprinter makes sense.

Re:Teach it!

[QuantumG]

If Apple tried to sue, Woz would likely pay for your defense.

Re:Teach it!

[SimonGhent]

Really? I am not sure about that, it would effectively be telling them to to not use what was available to them. Should we also deny access to color? I understand the need to write tight code, but not sure putting the equivalent of shackles on a sprinter makes sense.

Yeah, but runners sometime train with weights on to build strength. When they remove them their speed improves.

Re:Teach it!

[Junior J. Junior III]

True, but if not even the creators nor their company held an actual copy any longer, when what right should they have to the copyright?

Re:Teach it!

[3waygeek]

There's a simple solution; post it as a hex (or binary or octal) dump. You can then claim that it's just an excerpt of the first trillion or so digits of pi. By the time Apple's lawyers determine it isn't, the guys who decoded & published it will be long dead.

Re:Teach it!

[morgan_greywolf]

How long is copyright nowdays?

How old is Mickey Mouse?

Re:Teach it!

[Yungoe]

The way to get current students to be comfortable in small memory environments is to have the write code for microcontrollers.

Re:Teach it!

[repvik]

Yes! Like Rock Lee in Naruto: http://www.youtube.com/watch?v=06wLqMNn3co

Re:Teach it!

[Digital Vomit]

There you go trying to inject common sense into the Litigation Industry. Tsk, tsk, tsk.

Re:Teach it!

[Zaatxe]

How old is Mickey Mouse?

80 years this year. I get your point, but Wikipedia says that copyright usually last between 50 and 100 years after the creator's death. Walt Disney died in 1966, that is 42 years ago.

Re:Teach it!

[Anonymous Coward]

Hopefully a court would rule it "fair use", based on the four factors for determining such in the USA.

1. Purpose: It's provided for the purpose of discussion.

2. Nature: There aren't many other ways of expressing the non-copyrightable ideas underlying the code.

3. Amount: The code is posted in it's entirety. (I assume. Couldn't RTFA.)

4. Effect: None. The work has no remaining commercial value.

3 out of 4 ain't bad...but one never knows how a court will rule.

Re:Teach it!

[Two9A]

I believe the GP's point was that copyright will be extended by Congress as long as Mickey Mouse exists. Thus, the length of copyright is approximately the age of Mickey: this will hold true into the foreseeable future.

Re:Teach it!

[rirugrat]

Seeing that the Apple I was made out of parts that Jobs and Woz stole from Atari, I imagine there's copyright violations all over the place!

Re:Teach it!

[Anonymous Coward]

Wouldn't you mean 'how long was copyright when the code was developed'?

Re:Teach it!

[Anonymous Coward]

Of course I would! But this gets sticky. I gave away the Apple I schematics and monitor ROM (256 bytes to replace a front panel with a keyboard) but only a couple of copies of the BASIC, which I also intended to be in the open domain. I don't know if I ever gave away the completed Apple I BASIC because by then it was virtually the same for the Apple ][ (now completed) as well. We took the steps to retain the copyright for BASIC on the Apple ][. Any steps we took for the Apple I would be in the gray. I can't believe that it matters to Apple at all anyway.

Re:Teach it!

[operagost]

The copyright on "Steamboat Willie" is held by the Disney corporation, not Walt Disney's estate. You have to follow the corporate law, which I believe is an outrageous 95 years from publication now.

Re:Teach it!

[object88]

You can then claim that [the hex/binary/octal dump is] just an excerpt of the first trillion or so digits of pi. By the time Apple's lawyers determine it isn't, the guys who decoded & published it will be long dead.

Lawyer1: Is the first digit "3"?

Lawyer2: No.

Lawyer1: UNLEASH THE HOUNDS!!

Re:Teach it!

[flyspagmon]

This is spooky.. Woz.. Is that you?

Or maybe it just was..

Re:Teach it!

[Technician]

Wouldn't you mean 'how long was copyright when the code was developed'?

Good question. For the answer, it doesn't matter. Ask the same question of Walt Disney about Mickey Mouse. It's the same copyright law. I think Mickey is older than Apple Basic.

Electron ROM Ripping, ol' school

[ga5p0d3]

Reminds me of my housemate and I at university ('92-'95) using the tape control relay on an Acorn Electron wired to a PC serial port to rip the ROM so we could start writing an emulator. A small BASIC program PWM encoded the whole ROM in about an hour IIRC. Was a great start to the project, we got as far as CPU emulator, multi-window debugger, VGA display driver, and had it running basic no problems. He got it reading WAV's of games recorded from tape too. Got as far as the in-game screen of Chuckie Egg before we ran out of knowledge and became stuck trying to fathom the hardware keyboard input. (for the BASIC interpreter we just injected characters into the key buffer). Ahh, happy days. :o)

Re:Electron ROM Ripping, ol' school

[Anonymous Coward]

There is now a Free Software Acorn Electron emulator called ElectrEm:
http://electrem.emuunlim.com/

Unfortunately a GNU/Linux port of the new codebase version does not exist yet. Someone please contribute that the project. The graphics code is written for Simple Directmedia Layer (SDL), so this emulator should be quite straightforward to port.

Re:Electron ROM Ripping, ol' school

[EmagGeek]

92-95 is "ol' school?"

God, I feel old now...

I had a TRS-80 Model 1 with the 600-baud cassette (I think it was 600 anyway). I still have boxes of tapes for old games and software. I'd love to pull some of those off and see if I can emulate them. Talk about fond memories of the late 70's and early 80's...

Re:Electron ROM Ripping, ol' school

[ga5p0d3]

No, the hack was 'ol school, not when it was done. ;o) If it makes you feel any better, my dad and I were modding teletype machines to use as printers for our Interak 1 home built Z80 modular computer back in the 80's.

(I keep meaning to get round to ripping all the old code I wrote for my ZX Spectrum stored on a load of C15's so I can have an emulator powered trip down memory lane.)

Re:Electron ROM Ripping, ol' school

[Anonymous Coward]

ROM Ripping.

Ok - a rip is one way, right?

Rip a DVD - you can't reburn it, but I think that with a ROM you can.

EEPROM?

Re:Electron ROM Ripping, ol' school

[Nefarious Wheel]

92-95 is "ol' school?"

God, I feel old now...

I had a TRS-80 Model 1

I pre-date the integrated circuit, you insensitive clod!

Nobody will ever use more than 640 vacuum tubes on a single storage frame...

Re:Electron ROM Ripping, ol' school

[CountBrass]

"Vacuum tubes"? You were lucky, we had to play Space Invaders on an abacus made from a handful of hot gravel. And if we missed a single alien our father would flay us alive!

Re:Electron ROM Ripping, ol' school

[Nefarious Wheel]

You think you had it bad? We had to play Pong with wooden mallets!

Re:Electron ROM Ripping, ol' school

[Megane]

It was 500 baud. I've done a similar thing trying to read some of my own Model I tapes, but noise makes the simple decoding mechanism in TFA not work so well. (The Model III used 1500 baud)

I've also done some experimenting with Apple II and C-64 GCR decoding with a Catweasel board (FM/MFM already having been handled quite well), and the C-64 GCR is a lot harder to keep in sync because it doesn't have address-mark-only nibbles.

Re:Electron ROM Ripping, ol' school

[Dogtanian]

Also bear in mind that the Electron itself was a much older machine- it came out circa 1983. It was a much cut-down (but far less expensive) home-oriented version of the 8-bit BBC Micro, which was a very popular computer in British schools throughout the 1980s.

Unfortunately, the Electron wasn't a success; apparently this is because they had manufacturing problems and were unable to meet the demand when the machine came out- and by the time they'd got them fixed everyone else had bought other machines and the moment had passed.

Re:Electron ROM Ripping, ol' school

[Anonymous Coward]

Zug uhg? Zug mog og! Og dum mah!

Re:Electron ROM Ripping, ol' school

[operagost]

You had mallets? I still have the welts on my body from my Pong-playing days. It was a relief when I missed! In the 1980s, we couldn't afford an NES so I had to play "Contra" on the proving grounds of the local army base-- with live ammo!

Re:Electron ROM Ripping, ol' school

[DarthBart]

500 Baud. You could go to 1500 baud if you had a Model 3

Re:Electron ROM Ripping, ol' school

[WithLove]

Ok - a rip is one way, right?

Who told you this?

Very interesting

[Dan East]

I have a TI-99/4A that has been dead for nearly two decades, along with several hours worth of data stored on cassettes. I would love to recover the data off of those tapes. Most of it is the type of stuff a 10 year old would write in TI BASIC (and Extended Basic!), and it would really bring back some fond memories and certainly some good laughs.

Are there any generic utilities that can extract binary out of low-baud modem audio files? With the advantage of performing various audio processing and analysis in a non-linear, non-realtime manner, certainly data could be extracted by modern software that not even the actual legacy computer could decode.

Re:Very interesting

[clickety6]

http://www.cs1er.com/

Re:Very interesting

[zakezuke]

I have a TI-99/4A that has been dead for nearly two decades, along with several hours worth of data stored on cassettes. I would love to recover the data off of those tapes. Most of it is the type of stuff a 10 year old would write in TI BASIC (and Extended Basic!), and it would really bring back some fond memories and certainly some good laughs.

Are there any generic utilities that can extract binary out of low-baud modem audio files? With the advantage of performing various audio processing and analysis in a non-linear, non-realtime manner, certainly data could be extracted by modern software that not even the actual legacy computer could decode.

I'm sure there are emulators for the TI there. I met a few that came with a pretty complete cartridge collection including extended basic. Copyright is bound to be a little querky as there is TI stuff and there is Geneve. I think TI might have given up on their copyright, since their stuff has NO commercial value presently save the speech synthesizer.

http://www.mrousseau.org/programs/ti99sim/README.html

Claims to be able to convert .wav file TI files to binary.

But it's rather funny, the TV tape drive was pretty fast by the standards of the time. Many a time I transfered programs to answering machines.

Re:Very interesting

[sheph]

There are emulators, along with ROMS available. V9T9 is what I used until I went to XP 64x. Bring your cassettes into WAV files and read it in just like you're running it from tape. It'll run in a vpc, but then I discoved this cool thing called MESS. Every console you could ever want to emulate is in there, but the catch is that you have to find the console roms, and the game roms on your own. Google is your friend though.

Re:Very interesting

[Mr Z]

Slightly OT, but will it decode this copy of Pirate Adventure? ;-)

Re:Very interesting

[zakezuke]

Slightly OT, but will it decode this copy of Pirate Adventure? ;-)

You'll have to try.

At first I thought this was a serious post, since Scott Adam's adventures were a bit of a pain in the fact that if you loaded the game with tape, you could only save with tape. There was no obvious way to take the tape and put it on disk.

One statement I found amusing and frustrating was the comment on piracy. It was my first PC so I was kind of vague on piracy, but it was clear that they didn't want you buying the Adventure games and copying them. Fair enough, except no bugger sold them, and I didn't know anyone who had them. So, it was rather moot.

At this point, you can get all the Adventures from Scott Adams him self for the PC for free with the exception of Return to Pirates Isle which was for the TI exclusively, and RTPI 2 which is a 21st century release for the PC and not free.

So while this was a joke, I'm sure there were a few people who actually did want to convert tape to disk. I wasn't aware of a utility at the time that would do this.

Re:Very interesting

[Mr Z]

Sorry, I didn't mean to mislead you. :-) That's why I had the ;-) in there. I still think that that was an amusing use of the audio from that tape.

The Scott Adams adventures irritated me greatly back in the day. I could never get very far and gave up quickly. Maybe now that I'm 20+ years older, I'll appreciate them better.

I do have some of my classic crappy games on cassette that I wrote. I'm still kicking myself, though, for my accidentally taping over my crowning achievement of the era: Tank Wars. It was my TI Extended BASIC attempt at a tank battle game, but with even bigger tanks! :D

And then there's all my Music Maker compositions. Music Maker was a blast. Why the hell did it save all 14K of usable VRAM to tape for even the shortest composition?

Re:Very interesting

[zakezuke]

Sorry, I didn't mean to mislead you. :-) That's why I had the ;-) in there. I still think that that was an amusing use of the audio from that tape.

Well, keep in mind that you presented what was a legit question, which at the time you got a "you can't get there from here" answer.

1) The program didn't support tape to disk
2) The OS or disk utility didn't support tape to disk
3) TI computers went tits up
4) Scott Adams adventures went tits up

I gave the problem some thought, but the only means I knew of at the time to convert tape to disk was perhaps the use of "Terminal Emulator II", and upload the tape to a site, and then download. But IIRC TE-II didn't support upload with protocol and BBSs were in short supply in 1982-1983. I tried using compuserve, but they complained I was trying to pirate the game, the game that you could only play with the cartridge, which happened to come with the game.

It is however an amusing use tape, and you have to respect the geek who knows based on sound which game it came from.

The Scott Adams adventures irritated me greatly back in the day. I could never get very far and gave up quickly. Maybe now that I'm 20+ years older, I'll appreciate them better.

This is why it was so easy to believe that someone out there might have a save game they wanted to continue playing, though the sad truth is it would be easier to just start from the very start.

Those games were a bit of pain in the fact that often times the barrier wasn't so much figuring out the puzzle, but figuring out how to get the game to parse what you want to do. I remember Mystery Fun House where I was stuck trying to use the gum on the stick to get the coin.

http://www.msadams.com/downloads.htm

And then there's all my Music Maker compositions. Music Maker was a blast. Why the hell did it save all 14K of usable VRAM to tape for even the shortest composition?

Something to do with the fact that anything being processed by the graphics processor needing to be compiled first. Keep in mind that we are talking a first generation home computer, and it was impressive enough that the program allowed you to save your compositions. This wasn't the norm at the time.

Re:Very interesting

[Mr Z]

Something to do with the fact that anything being processed by the graphics processor needing to be compiled first.

Somehow I doubt it. The TI Home Computer did keep its data in video RAM, and a great bulk of TI programs were written in Graphics Programming Language (GPL), an interpreted language and stored on serial ROM. Even TI BASIC was written in GPL. Video RAM wasn't directly accessible by the CPU. It was accessed through a register window on the VDP. GPL provided abstractions that made it easier for programmers to code despite this indirection. This combination of indirect addressability and interpreted code is probably what you're thinking of.

But that doesn't cut it as an explanation for why Music Maker stored pretty much the entire Video RAM, whereas other programs (including the built in BASIC) only stored what they needed. The routines were there for storing structured files in all sorts of formats. The only explanation that really works for me is laziness on the part of the programmers.

Since I work for TI now, I could probably ask around and find out if anyone knows who wrote Music Maker. :-) I know some guys who worked with the Home Computer folks. In fact, I was hired in by the lead logic designer of the TMS9995 CPU that was meant for the ill fated TI-99/8.

--Joe

Re:Very interesting

[zakezuke]

But that doesn't cut it as an explanation for why Music Maker stored pretty much the entire Video RAM, whereas other programs (including the built in BASIC) only stored what they needed. The routines were there for storing structured files in all sorts of formats. The only explanation that really works for me is laziness on the part of the programmers.

I have to admit, I'm fuzzy on the workings of the TI now it's almost 3 decades after the fact. In fact I could only say I thought the tape file for Music Maker was a tad bit bulky. Laziness I can accept. It's not like you could load tapes independent of basic or anything like that. I am curious so if you could find out I'd be interested.

While a tad sloppy on the music maker front, TI really had their shit together as far as putting together a platform during a time when people didn't know what you could use a home computer for.

Re:Very interesting

[Mr Z]

While a tad sloppy on the music maker front, TI really had their shit together as far as putting together a platform during a time when people didn't know what you could use a home computer for.

Well, yes and no. They definitely had more of a turn-key, consumer product focus. Unfortunately, their model consumer product was the Speak & Spell. With the Home Computer, they went into the toy business.

This is evident in many design decisions. The BASIC interpreter was slow for three reasons:

1. Not much CPU addressable RAM. You need an extra level of indirection to get to video RAM.
2. The BASIC interpreter was written in GPL, which was itself an interpreted language.
3. They added explicit delay loops on top of the above in the character I/O routines and a few other places.

I learned #3 from the guy that hired me into TI.

Have you ever wondered why text scrolled up the screen at about the rate of a printing calculator in TI BASIC, and you couldn't make it go faster? They didn't want stuff to scroll by too fast for beginners and children. So, they made it impossible to do from BASIC. I believe that's also why CALL HCHAR and CALL VCHAR are so slow, but that latter part is just a hunch.

TI Extended BASIC fixed many of these issues, but it was still rather slow. TI XB II, which would have come with the TI-99/8, appears to fix all those issues. I don't know--I've never gotten to play with it. It's notable though that the TI-99/8 announces itself simply as "Texas Instruments Computer," rather than "Texas Instruments Home Computer." The shift in mindset is a big thing.

Don't get me wrong: The 99/4A was the first computer I owned, and I loved it dearly. I learned assembly language using the Mini Memory cartridge and even wrote some BASIC extensions. (Mostly, 40 col character access from BASIC that was dodgy at best.) It was turn-key, air-tight and did just what it was designed to do. Unfortunately, that also probably figured largely in its undoing as well, especially in the era of the tinkerer.

Ironically, one of its competitors succeeded by being quite the opposite--a tinker friendly, open system, complete with schematics and source code for the PROMs. That company grew up to be one of the most successful suppliers of turn-key, air-tight, does-just-what-it-was-designed-to-do systems. That company's Apple.

Between the TI-99/4A and New Coke, though, I learned if Bill Cosby tries to sell me something other than Jell-O, it's a gonner. ;-)

Re:Very interesting

[zakezuke]

Well, yes and no. They definitely had more of a turn-key, consumer product focus. Unfortunately, their model consumer product was the Speak & Spell. With the Home Computer, they went into the toy business.

Well, not only was it a decent turn key solution, they released enough in the way of technical specifications to choke a horse. The system was released with tapes with instructions on how to program basic. Good instructions.

Education, Plato software was quite good and an agreement for 100 titles by September 1982, that's not too shabby.

I think it was their game place to sell software development packages on their mini computer, but that may have changed.

TI Extended BASIC fixed many of these issues, but it was still rather slow. TI XB II, which would have come with the TI-99/8, appears to fix all those issues. I don't know--I've never gotten to play with it. It's notable though that the TI-99/8 announces itself simply as "Texas Instruments Computer," rather than "Texas Instruments Home Computer." The shift in mindset is a big thing.

I had extended basic pretty much from the get-go. I only met a Tomy Tutor once.

Uhh...

[consonant]

Terrific fun for the whole family.

That must be one weird family...

Re:Uhh...

[Zaatxe]

That must be one weird family...

I have a 14-years-old step-daughter who is crazy about Star Trek. Families are sure weird.

Re:Uhh...

[Dr. Cody]

At least they're not walking into an agent's office to show him their act...

Re:Uhh...

[Anonymous Coward]

Is she hot?

Re:Uhh...

[Zaatxe]

I know this is a AC trolling, but she is actually very beautiful and popular, contrary to the Star Trek geek sterotype. Weird, huh?

Re:Uhh...

[pintpusher]

The Aristocrats!!

Re:Uhh...

[Anonymous Coward]

What would they call themselves?

Re:Uhh...

[Anonymous Coward]

Please invent a time machine and send her back to when I was 14 years old.

Assembler

[Anonymous Coward]

Seriously... teach assembler in school, with the same memory limitation... let them squeeze out the last bit of the hardware, just like the hackers did with Commodore 64.

9600 baud was common on C64

[Joce640k]

But that had a dedicated "digital" tape drive (ie. it was optimized for recording those sorts of signals, not music.

Javascript VM?

[Anonymous Coward]

So when will we actually see a javascript vm being able to execute it?

Nick Hodge Says

[Anonymous Coward]

(scroll down to the comments, in case you ever RTFA):

Apple Inc does own an Apple I

It is actually owned by Apple Computer Australia, and on loan and display at the Powerhouse Museum in Sydney.

For many years, it was under a glass box in the foyer of the Apple Australia offices.

Re:Nick Hodge Says

[argent]

I wonder if that was the one that was on display at Apple's only distributor in Sydney when I used to go in (damn, I can almost remember the bus lines I took) and write game programs on the display models in the back. They didn't have much software back then so they let kids write stuff and leave it running as an early "attract mode". There was an Apple I in a display case... it was never powered on when I was there.

Re:Nick Hodge Says

[Al Kossow]

Apple in Cupertino still should have one. It was on display for years in the Mariani I lobby. It was moved to IL5 when the new campus opened. The case also contained the wood model for the Apple III, a Lisa, and the prototype Apple II. The case was removed about five years ago. Hopefully, it's in a warehouse somewhere.

Re:Nick Hodge Says

[mattack2]

I think you really mean IL4. That's where the other computers were in the display cases, at least.

Memories

[buddhaunderthetree]

I tell my kids about loading programs off cassette tapes but they just don't get it. I guess they'll never know the agony of having a program ruined by fragility of magnetic tape.

Re:Memories

[troon]

Tape, yes. But do you remember 45rpm floppy 7" "records" that came with magazines? Or programs broadcast over the radio late at night?

I've just written this article, coincidentally:

http://mark.tranchant.co.uk/2008/07/a-unique-generation

Re:Memories

[stevey]

It was always bad on multi-stage games, where you loaded up levels on demand, and had to rewind and re-load earlier levels when you'd died!

I can still remember this error message:

R Tape loading error, 0:1

Re:Memories

[troon]

:-)

My sister used to hide behind the sofa whilst games loaded off tape, as she had developed a phobia for that error message! As an annoying little brat, I would sometimes subtly turn down the volume on the tape player until the Spctrum could no longer recreate the signal, and bombed out with that error.

Re:Memories

[anomnomnomymous]

I guess they'll never know the agony of having a program ruined by fragility of magnetic tape.

They never encountered a scratched (software) CD?

Re:Memories

[calidoscope]

IIRC, something like the March 1977 issue of Interface Age had what they called a "floppy ROM" - the 7" records you described.

I may be a bit off base here, but the Apple I tape formst precedes the Kansas City Standard (1200 baud FSK).

Re:Memories

[Vegeta99]

Kids use CDs?

Hell I thought they all used uTorrent because a $20/week allowance gets them like 4 games a year!

QAM

[tepples]

Still phase modulation at 9kbaud+ would be a tight fit on an audio tape. I don't think things like QAM would be possible given the size of the package

Quadrature amplitude modulation was in use in the 1960s: it's just two AM carriers out of phase by 90 degrees. The color encoding in NTSC and PAL used QAM.

Re:QAM

[Hal_Porter]

Still phase modulation at 9kbaud+ would be a tight fit on an audio tape. I don't think things like QAM would be possible given the size of the package

Quadrature amplitude modulation was in use in the 1960s: it's just two AM carriers out of phase by 90 degrees. The color encoding in NTSC and PAL used QAM.

This modem was potted circuit board. It had space for a couple of 8 pin chips a few passive components, all of which had to be available in the 80s, so we're talking OpAmps and 4000 series CMOS chips. It cost £20 so it the cost of the components had to be less than that. You're not going to build a QAM modem with those constraints.

Re:QAM

[mattack2]

It's also used to put 'digital cable' channels on cable. Devices with a QAM tuner don't need a cable box nor cable cards (for the unencrypted channels, such as the 'broadcast' channels on cable. http://en.wikipedia.org/wiki/QAM_tuner

MP3 ?

[XNormal]

The psychoacoustic models of MP3 compression must have done wonders for the ancient recording.

It's like compressing a bitmap of line art with JPEG.

Re:MP3 ?

[IhuntCIA]

My experience with C64 tapes says it does not. MP3 makes too much errors, and always ends up in LOADING ERROR. Never had an error with WAV file. No lossy data, compression no error.

Re:MP3 ?

[Eil]

The psychoacoustic models of MP3 compression must have done wonders for the ancient recording.

As long as the quality settings are high enough, I wouldn't think it would matter much. The encoding scheme is designed to survive a hostile medium. (Audio.) The original magnetic tape mangles the signal far worse than encoding it in MP3 does.

Although for archival purposes, yes, a lossless codec should always be preferred.

Pom1

[anarkavre]

I wrote, ahem, ported a Java Apple 1 emulator about a year ago to SDL and added a few of my own features. Haven't done much more to it since then. But for those nostalgic geeks out there, you can find it at the following link.

http://pom1.sourceforge.net/

Re:Pom1

[morgan_greywolf]

Hmmm....an Apple in Java....I'll have to try that.

*dunks a piece of Washington Golden Delicious in his coffee*

*munch*Not*munch*bad*munch*

Re:Pom1

[Anonymous Coward]

I also wrote an Apple1 emulator, in C, that works on the command line. http://sourceforge.net/projects/dinaao/

You can cut and paste basic programs into my emulator. 8^)

Woz Basic is included, as well as the Krusader 6502 assembler.

JG.

Amazed it actually works

[pslam]

The interesting thing about this article is:

• a) The MP3 encoding process didn't totally mangle the signal. A decent encoder should have dropped all those 1ms duration waves due to masking. Must be a crappy encoder or a forced high bitrate :)
• b) I get the distinct impression the author doesn't know what FSK is, or that it's the encoding for the signal. Yet he still manages to decode it. The HARD way.

This could have been done so much more easily :)

Re:Amazed it actually works

[Anonymous Coward]

That's what's cool... if you don't know any better, the way it was done, was as good as any.

Re:Amazed it actually works

[pla]

A decent encoder should have dropped all those 1ms duration waves due to masking.

a 1ms pulse (if you mean rise, 1ms hold, fall) corresponds to 500hz - Pretty much smack dab in the middle of the human auditory range.

Any encoder that filtered that out would most likely only appeal to bats and insects, who don't tend to write all that much audio processing code.

Re:Amazed it actually works

[pslam]

a 1ms pulse (if you mean rise, 1ms hold, fall) corresponds to 500hz - Pretty much smack dab in the middle of the human auditory range. Any encoder that filtered that out would most likely only appeal to bats and insects, who don't tend to write all that much audio processing code.

A 1ms pulse between two frequencies is below the threshold of what the human ear can resolve when the tones are that close together. MP3 takes advantage of that by treating the transitions as masked and quantizes it heavily. If encoders didn't use this masking trick, they wouldn't be anywhere near as effective.

It's probably half the reason why the signal looks incredibly distorted. What's good enough for human ears may look messed up if it was supposed to have been a data stream.

Re:Amazed it actually works

[fm6]

You obviously know more about DSP than I do (which doesn't say much!) but perhaps the non-mangling has to do with the fact that the signal is not 1200 baud. As I recall, cassette tape interfaces recorded at 110 baud.

An interesting mistake. The author would seem to be somebody who is old enough to remember 1200 bps modems (technically, not 1200 baud, though most people called them that) and just can't conceive of any data channel being slower than that!

Re:Amazed it actually works

[spaceyhackerlady]

That's what's cool... if you don't know any better, the way it was done, was as good as any.

In industry we call this "re-inventing the wheel". Writing an FSK demodulator is really not a major achievement.

...laura

Re:Amazed it actually works

[Detritus]

Amateur packet radio commonly uses Bell 202 style modems, which are both 1200 bps and 1200 baud, only half-duplex. I believe they are also commonly used in credit card verification terminals. The Bell 212A was full-duplex, 1200 bps, and 600 baud.

Microcontrollers

[tepples]

Really? I am not sure about that, it would effectively be telling them to to not use what was available to them.

As long as there are integrated circuits, there will always be dirt-cheap microcontrollers that don't have a lot of ROM and RAM available to them.

Period shift keying

[tepples]

I get the distinct impression the author doesn't know what FSK is, or that it's the encoding for the signal. Yet he still manages to decode it. The HARD way.

The author treated it as period shift keying, which is equivalent to frequency shift keying. What makes decoding an FSK signal in the period domain "the hard way"?

Re:Period shift keying

[pslam]

The author treated it as period shift keying, which is equivalent to frequency shift keying. What makes decoding an FSK signal in the period domain "the hard way"?

It's not quite equivalent. The recorded wave file is heavily bandlimited so you can't reliably use a comparator to convert it to a period shift signal. I suspect the MP3 conversion is a lot to do with that. If there were any noise around the zero-crossing point, it wouldn't work at all. He's lucky that method works.

Re:Period shift keying

[IhuntCIA]

I suspect the MP3 conversion is a lot to do with that. If there were any noise around the zero-crossing point, it wouldn't work at all. He's lucky that method works.

He is more lucky than he knows. I never ever made working MP3 out of working WAV for my C-64. It simply wont load correctly. If I look the signal using the head azimuth analysing program MP3 looks just like the head azimuth is bad all the time.

There is a MUCH Easier Way...

[macs4all]

I own an Apple 1. ...And a copy of Apple 1 BASIC on cassette, and Woz's Mini-Assembler that is "origin-ed" for the Apple 1. (This is the same Mini-Assembler that was in the Apple ][ ROMs, at $F666). And a few other Apple 1 goodies.

Do you realize that the cassette interface for the Apple 1 and the Apple ][ are identical?

Yep, you can read an Apple 1 audio cassette with any old, easy-to-find Apple ][. And from there, you can use any one of a million methods to get the data out of memory and onto another medium.

Also, you can simply use the Apple ][ to create a NEW cassette for your Apple 1 (if you happen to be lucky enough to have one).

BTW, I think mine is "serial number" 0064. At least that's what I think the "0064 that is written in Sharpie on the PC board means...

Re:There is a MUCH Easier Way...

[Stavr0]

Pics or it didn't happen... But seriously, I would love to see shots of your Apple I

Re:There is a MUCH Easier Way...

[macs4all]

Actually, I ran across some pix I shot of my Apple 1 a few weeks ago on an old PowerMac 8500 that I still turn on occasionally. If I can figure out where to post them, I will.

I also have a copy of the original Apple 1 Cassette Interface (it was a OPTION!) literature, with the oh-so-cool "Newton's Apple" logo on it. I may or may not have taken a pic or scanned that yet. I still have it, though. Along with the "replacement" Apple 1 owner's manual (has a tan cover, with an at that time "modern" Apple logo on it) sent to me personally by Woz himself (sorry, no autograph, dammit!).

And for the piece-of-resistance, I have this HUGE collection of Woz's notes on developing the Apple 1 and ][, and the cassette interface (with an in-depth description of the theory of operation of the cassette hw and sw) (which is 1800 baud, btw, not 1200), as well as some of his notes when he was developing Integer BASIC and the Floating Point package and the Sweet 16 pseudo-processor in the Apple ][ (but not in the ][+ or beyond). This collection of notes used to be called "The Woz Pak". Mine was actually mailed to me (at the same time as the Apple 1 manual, above) by Woz himself. Again, no autograph. Boy, was *I* stupid, or what?!?

The Woz Pak is about 250 pages of pure geek heaven. Now I'll have to dig it out and read it again!

Wonder how much IT'S worth? Kinda like having a copy of da Vinci's notes...

Re:There is a MUCH Easier Way...

[Anonymous Coward]

I own an Apple 1. ...And a copy of Apple 1 BASIC on cassette, and Woz's Mini-Assembler that is "origin-ed" for the Apple 1. (This is the same Mini-Assembler that was in the Apple ][ ROMs, at $F666). And a few other Apple 1 goodies.

Do you realize that the cassette interface for the Apple 1 and the Apple ][ are identical?

Yep, you can read an Apple 1 audio cassette with any old, easy-to-find Apple ][. And from there, you can use any one of a million methods to get the data out of memory and onto another medium.

Also, you can simply use the Apple ][ to create a NEW cassette for your Apple 1 (if you happen to be lucky enough to have one).

BTW, I think mine is "serial number" 0064. At least that's what I think the "0064 that is written in Sharpie on the PC board means...

Hey!

This is not ebay!

Even though some people around here would bid to buy it :P

Re:There is a MUCH Easier Way...

[moosesocks]

Grab a Flickr account, and upload the photos there.

Having scans of that book preserved somewhere for posterity would be pretty freakin' awesome too. I sincerely doubt Woz would mind...

This is your chance to be a geek hero. Share the wealth!

Re:There is a MUCH Easier Way...

[macs4all]

I keep referring to it as "My nest egg", LOL!

Yeah, posting pix of it and the other stuff has been on my long To Do list for a long, long time.

Maybe this will be the year...

Re:There is a MUCH Easier Way...

[Anonymous Coward]

$63078? Seems pricey...

Those were the days...

[Digital_Mercenary]

Many seasons ago, in a high school computer lab in the Bronx. I would save programs from computer labs Commodore PET to tape and wonder why they would always be blank the next day. Over time I realized that riding the NYC trains with my school bag on the car floor was not such a cool idea. NYC trains were somehow erasing the tapes when they were place closed to the floor. Until I figured this out there were many nights spent pondering what the gods of computing had against me. Curse you Number 6 Line! Curse you!!!

"Ahhh the suffering...."

Re:Those were the days...

[Gordonjcp]

That's because they're electric trains with big spinning magnets ;-)

The BBC used to get people to take taxis rather than use the Underground, for the same reason.

Re:Those were the days...

[Detritus]

It's those traction motors. They are notorious for emitting a magnetic field that is strong enough to erase magnetic tape. If they can move a train, they can erase your tapes. The same thing used to happen to couriers transporting 9-track magnetic tapes in NYC via the subway.

So how will Apple react to this?

[sunny256]

This is way cool. But we have seen lately how strict Apple behaves when unlocking iPhones, etc. Wouldn't it be ironic if Apple sues this guy for copyright infringement and pushing the DMCA instead of being thankful that he recovered this piece of history?

Re:So how will Apple react to this?

[CountBrass]

Wouldn't it be "ironic" if Apple gave him a billion dollars in cash and elected him life-time president of the world. There, see, random speculation is both easy and worthless.

Re:So how will Apple react to this?

[BBird]

and so are pointless replies. grand-parent makes you think. yours (parent) does not.

Re:So how will Apple react to this?

[argent]

Wouldn't it be ironic if Apple sues this guy for copyright infringement and pushing the DMCA instead of being thankful that he recovered this piece of history?

It would be extremely unlikely. Apple has to respond promptly to schemes that bypass controls that they are are contractually obligated to provide. They have not, so far as I know (and I've used Apple computers almost as long as there have BEEN Apple computers) ever shown any interest in chasing after people over ancient legacy stuff.

Re:So how will Apple react to this?

[pcfixup4ua]

They can't do that, they are not Microsoft!

Re:I don't get this bit...

[sjaskow]

The negative sample is probably right. If you look at the wave form sample, you can see where it drops. I think he's looking for errors in the data from the tape.

The command line is simple the is to redirect stdout to the output file of choice.

Small is beautiful

[sunny256]

I think that at least the basic interpreter should be taught to the new generations. They don't feel confortable enough in less than 1 GB, what if they had just 4 KB?

Anyone remember Turbo Pascal 3.02? It had a pretty decent editor, compiler, overlay support and was able to create .COM files by copying parts of itself into the compiled file. And everything packed together in a single .COM file of 37 kilobytes. Impressing. Check out The Borland Museum and have a look for yourself.

They really knew how to create small and elegant code in those days. I'd like to have the assembly code for that, just for fun and inspiration.

Re:I don't get this bit...

[Anonymous Coward]

The negative sample is probably right. If you look at the wave form sample, you can see where it drops. I think he's looking for errors in the data from the tape.

That doesn't make sense in the context of the program though. If you look at the code, the if clause I asked about does --direction, the variable is initialized to 1 and there's a check...

If (!direction) {
// blah
  ++direction;
}

So if direction is less than 1 then it hits the if statement I wrote about and becomes --direction. My guess is it's to handle silence at the end of the sample data and the if statement I posted about is actually...

if (sample < threshold)

Which is very strange... since direction will never be greater than 1 it may as well be a break/return.

I know about the command line, the original was...

cat apple1basic-mono.wav | ./apple1basic-decode > apple1basic.bin

I was curious about why someone why write it like that.

Re: TurboTape

[DaveP in Ohio]

I ran TurboTape for the Commodore64 for quite a while... You actually had to enter the program using Compute's special assembly entering program, the name is eluding me at the moment (It was over 25 years ago!)... the early release had an error that blew 7414's so I had to replace them a couple of times in the datasette. Amazing that a single incorrect byte in the assembly could take out hardware.

Why they didn't use MESS?

[marcomarrero]

MESS emulates the Apple I, can read WAVE files, and the entire source code is available. :)

I miss my old CoCo3, but I hated cassette tapes. The saddest thing is that Audio Cassettes were designed to be lousy as a data storage media - they used two sides (interference), and were created to record just human voice. The only other option were floppy drives, and back then they were expensive and/or overpriced ($200 and up) which is equivalent to $400+ now in 2008. Most drives had to include the entire controller I/O inside the unit, and probably also a disk OS.

Some people STILL haven't learned

[Anonymous Coward]

Back in the TRS-80 Model 1 days, I wrote a bunch of BASIC arcade style games. The tapes are long lost, destroyed, or unreadable. But even then, I was smart enough to PRINT. I can easily read them today, and the only device I need is a pair of reading glasses. I could even easily load them into an emulator running on modern hardware using OCR software.

There's nothing like a good old hardcopy.

6502 assembly - now there's a blast from the past

[GogglesPisano]

I disassembled a few dozen bytes of the dump to see what it looked like. I have no idea what it's supposed to be doing, but seeing the code does take me back a few decades...

E000 4C B0 E2 JMP $E2B0
E003 AD 11 D0 LDA $D011
E006 10 FB BPL $E003
E008 AD 10 D0 LDA $D010
E00B 60 RTS
E00C 8A TXA
E00D 29 20 AND #$20
E00F F0 23 BEQ $E034
E011 A9 A0 LDA #$A0
E013 85 E4 STA $E4
E015 4C C9 E3 JMP $E3C9
E018 A9 20 LDA #$20
E01A C5 24 CMP $24
E01C B0 0C BCS $E02A
E01E A9 8D LDA #$8D
E020 A0 07 LDY #$07
E022 20 C9 E3 JSR $E3C9
E025 A9 A0 LDA #$A0
E027 88 DEY
E028 D0 F8 BNE $E022
E02A A0 00 LDY #$00
E02C B1 E2 LDA ($E2),Y
E02E E6 E2 INC $E2
E030 D0 02 BNE $E034
E032 E6 E3 INC $E3
E034 60 RTS

Back in my C64 days, I used to practically think in 65xx assembly code... ah, memories.

Two people?

[sootman]

Surprised none of the other grammar nazis* picked up on this:

"...neither Steve nor Woz..."

Erm, isn't Steve Wozniak one person?** Perhaps he meant "...neither Jobs nor Woz..."?

* sorry if I mis-capitalized/mis-punctuated "Nazi's"

** spare the fat jokes

Re:Two people?

[danzona]

"...neither Steve nor Woz..."

Erm, isn't Steve Wozniak one person?** Perhaps he meant "...neither Jobs nor Woz..."?

Steve Jobs is another person, so I guess it is technically correct. Maybe the people at pagetable.com are on first name / nickname basis with Steve Jobs and Steve Wozniak, and they just type they way they talk.

Re:Two people?

[Anonymous Coward]

> Perhaps he meant "...neither Jobs nor Woz..."?

Who calls Steve Jobs by his last name?

Kansas City Standard

[fragMasterFlash]

I thought that cassette storage for Apple computers was based on the Kansas City Standard http://en.wikipedia.org/wiki/Kansas_City_Standard/? Get off my lawn

Re:Kansas City Standard

[macs4all]

Nope. Woz rolled his own standard. MUCH faster and MUCH more reliable than the Kansas City standard.

In fact, of all the cassette interfaces of the day, including some REALLY elaborate S-100 ones developed by Don Tarbell, the Apple 1 (and Apple ][) cassette interface stands alone in reliability and "forgiveness" to things like playback level and tape quality. That is because Woz depended SOLELY on the timing of ZERO CROSSINGS of the signal, which, unless the tape speed is enormously out of whack, or enormously unstable millisecond-to-millisecond, have ZERO (pun intended) effect.

I have some original engineering notes by Woz regarding his development and testing of the cassette interface, where he describes his own amazement at how reliable his cassette interface is. He describes hunting down the cheeziest recorders, and the most horrible cassettes, to try it on, and it works like a charm. It just also happened to be either the fastest, or the second fastest (and easily the most reliable!) of anything available. Before or since.

Re:6502 assembly - now there's a blast from the pa

[macs4all]

Let's see how my memory serves:

$E000 - BASIC Coldstart

$E003 - Wait for a key (wait for bit 7 "set" of address $D011), then Load Accumulator with the ASCII keycode (from location $D010), and Return.

$E00C - (Do Uppercase conversion on ASCII, I think), and Jump to the CharOut routine ($E3C9).

$E018 - Looks like the "scroll" routine. That #$8D is a Carriage Return char (Apple 1 and ][ 'ASCII' always had bit 7 SET). The Apple 1 had a "TV Typewriter"-style interface (with apologies to Don Lancaster), that used some "odd" Fairchild shift-registers for the "screen memory". There was no such thing on the Apple 1 as "VTAB()" or "HTAB", or the "BASECALC" routines in the Apple ][ monitor. In fact, there was no random access to the screen position at all. That's why the scroll routine looks like it is simply re-writing stuff to CharOut. It is...

As an interesting aside, my copy of Apple 1 BASIC, which is from May, 1976, nonetheless does NOT give a "SYNTAX ERR" when given the following Apple ][ Integer BASIC verbs: "COLOR=", "PLOT", and "HLIN" (but not "VLIN", which returns an error). This says to me that Woz was already heavily into developing the Apple ][ even when the Apple 1 was barely on the market, so to speak. It would be interesting to find out if other owner's versions of Apple 1 BASIC respond to more, or less, Apple ][ BASIC commands...

The decoder uses a Schmitt trigger

[tepples]

It's not quite equivalent. The recorded wave file is heavily bandlimited so you can't reliably use a comparator to convert it to a period shift signal.

Which is why the decoder uses two comparators: one at 32768/DIVISOR and one at -32768/DIVISOR. In order to count a pair of transitions, the decoder has to see the waveform cross below the negative threshold and then above the positive threshold. This Schmitt trigger provides a bit of hysteresis that cleans up the signal. The value of this DIVISOR corresponds to the tape deck's volume control.

If there were any noise around the zero-crossing point, it wouldn't work at all.

Such noise is what the DIVISOR is supposed to filter out. I disassembled parts of the Apple II BIOS once, and it turned out that the original Apple I/II cassette interface also implemented period shift keying.

He's lucky that method works.

If there were more noise than the DIVISOR could reject, then wouldn't it fail to load on the original hardware too?

Re:The decoder uses a Schmitt trigger

[pslam]

That's nice but,

Which is why the decoder uses two comparators: one at 32768/DIVISOR and one at -32768/DIVISOR. In order to count a pair of transitions, the decoder has to see the waveform cross below the negative threshold and then above the positive threshold. This Schmitt trigger provides a bit of hysteresis that cleans up the signal. The value of this DIVISOR corresponds to the tape deck's volume control.

He doesn't do that.

Such noise is what the DIVISOR is supposed to filter out. I disassembled parts of the Apple II BIOS once, and it turned out that the original Apple I/II cassette interface also implemented period shift keying.

He doesn't do that

If there were more noise than the DIVISOR could reject, then wouldn't it fail to load on the original hardware too?

Yes, he's lucky.

Re:The decoder uses a Schmitt trigger

[tepples]

the decoder uses two comparators: one at 32768/DIVISOR and one at -32768/DIVISOR.

He doesn't do that.

Read the code in the article. I'll summarize the relevant part:

if (sample > (32768/DIVISOR)) {
// handle positive transition
} else if (sample < -(32768/DIVISOR)) {
// handle negative transition
}

That looks like a Schmitt trigger to me.

Re:6502 assembly - now there's a blast from the pa

[Simon Rowe]

Back in my C64 days, I used to practically think in 65xx assembly code... ah, memories.

The sad thing is I was able to disassemble the first few lines from memory. How come I knew 4C was JMP when I can get to the top of the stairs and forget what I went up for?!?

In Federated Brazil...

[Tetsujin]

the idea was to make talk radio accessible to def people.

Like Mos Def and Def Leppard?

Re:I don't get this bit...

[Anonymous Coward]

I was curious about why someone why write it like that.

Fairly standard cat abuse. Nothing to be alarmed about.

Re:6502 assembly - now there's a blast from the pa

[S-100]

E020 A0 07 LDY #$07. Aaaah. The memories!

is there one at the Santa Clara Computer Museum?

[peter303]

I think I saw one there, but that was two years ago. At the time the Googleplex had just taken over the other half of the old SGI building and threatened to devour the rest of the SGI campus.

When the two Steves showed off their Apple-1 at the SLAC Homebrew Club in the 1976 they has it in a wooden case, I recall seeing.

Woz

[Anonymous Coward]

Actually does own an Apple I, unless he gave it away in the last week.

Neither Steve nor Woz owns an Apple I?

[SteveWoz]

I still own a couple Apple I's.

Re:Neither Steve nor Woz owns an Apple I?

[/dev/trash]

I thought that the assertion that you didn't seem, I dunno, a little off.

Re:Neither Steve nor Woz owns an Apple I?

[Anonymous Coward]

Holly raptor jesus... Steve Wozniak reads slashdot like a normal geek! I would have thought being a god like him he would know it all and if he didn't he could just have it beamed into his head...

Re:Neither Steve nor Woz owns an Apple I?

[pawperso]

"I still own a couple Apple I's." Can I have one please :)

Re:6502 assembly - now there's a blast from the pa

[vonhammer]

Didn't the terminator run on 6502 assembly? I seem to recall watching a scene where they scrolled a bunch of assembly as the guvanator was deciding how to answer a question. I was sure I saw a load accumulator instruction in there somewhere! Thanks for the memories.

Re:6502 assembly - now there's a blast from the pa

[macs4all]

I remember that display, too.

Yes, it was definitely 6502 assembly. Even scrolling by that fast I caught some of the code.

Re:6502 assembly - now there's a blast from the pa

[tgd]

Ha, I did the same thing. Glad I'm not the only one.

And strangely I'm sure I haven't touched 6502 in 25 years. Strange the little things you remember. I did a lot of programming on the Atari platform and I'm sure if I stopped and thought about it I could remember enough details of using the Pokey to generate sound or tricks in the CTIA/GTIA to still be able to write code to put a few different video modes on screen at once.

Those were the days.

I feel special

[AncientOfHerb]

We built an Apple 1 in my electronics class back when I was in high school. I had not realized they were so rare :)

FYI

[glitch23]

It is spelled archaeology, not archeology. I'm surprised no one caught this or maybe no one cared enough. Seeing as how we have some BSD folks here I would think that the missing 'a' would have been obvious since 'daemon' is spelled and pronounced the same way.

Apple I BASIC in .wav file

[monzsca]

I built a replica apple I with cassette interface a few years ago using kits of parts sold on ebay (following the original design). I was able to to load apple 1 basic, via a serial interface, too much to type, and successfully save it to tape (computer sound card) and load it back. I have the audio file here.

GFA BASIC

[bollox4]

Got to put Apple aside to flagwave the excellent GFA BASIC which ran in interpreted mode decently and when compiled quite close to C compiled. It ignored line numbers (an advance in those days for a BASIC) and in later versions included matrix operations. It was also very easy to learn partly down to the decent manual. Perhaps I recall this wrongly but I'm sure the GFA Interpreter only version was included free on magazine cover discs.

And to make it up to date

[Askmum]

You write the audio to an audio CD so that the signal won't detriorate.