The Apple II: The Machine That Started It All

Thomas Hormby writes "The first Apple II was sold on June 5, 1977. It was outfitted with a 1 mhz processor, 4 KB of RAM, a keyboard and a cassette interface. Despite the seemingly paltry specs, the machine made Apple, and bankrolled the LISA, Macintosh and LaserWriter. Besides building Apple, the machine revolutionized the entire microcomputer business, pulling it way from the hobbyist kits and closer to todays PC. Read about it at MLAgazine."

Comments

wrong on at least some details on cassette storage

[call -151]

In order to make machine readable cassettes, the user had to use a very sensitive tape recorder. Besides the recorders, users also had to buy media, which was way more expensive than standard floppy disks.

Sorry- that wasn't the case. Commodity standard cassette recorders worked really well for storing Integer BASIC and machine language code and they used ordinary cassette tapes that were way way cheaper than floppies, particularly at that time.

Apple II innovations

[goombah99]

I worked in a computer shop selling computers at the time the apple II came on the scene. The brands around then were Imsai, cromenco, Sol, Northside, and even an altair if you wanted one. With the exception of the comodore pet, they all ran on 8080, 8085 or Z-80.

All had traditional power gobbling transfomer-rectifier-capacitor power supplies. If they had a bus it was an enornmous S-100 bus. None had memory mapped I/O or could interleave graphics and text. If they had disks, they were hard sectored disks. And most important of all none used Dynamic memory natively. You could buy dynamic memory cards as S-100 plug ins but they were not reliable.

Unlike the 8080/Z-80 the 6502 had a symmetric instruction clock cycle and all so there was a free cycle where memory woas gaurenteed not to be accessed every other cycle dependably. (not true of the 8080) This meant you could use that interval to refresh the dynamic ram. Thus one never had to insert wait states or have flaky thing happen when there was an irregular refresh rate. It simply worked.

But Wozniak and co, were even more clever. Why waste that clock refresh? since the duration was the same as the regular memory fecth time, they made it a full fetch. But what fetch that had to increment repetiviely over the upper 8 bits of address space would be useful? The video memory! so they backsided the video memory fetch on that.

Contrary to today having memory mapped video was better than having th e video memory on a graphics card. On most grpahic cards when the CPU was accessing the memory they video card could no and you saw glitches. thus video updates were usualy timed by the CPU to occur in thehorizonatal and veritcal re-trace blanking intervals. very clumsy and slow.

Apple used a switching power supply. the first I had ever seen. it was small, and took up no room. the imsai, altair, cromenco and northside computer were huge and half of them were the power supply. some of the capacitors in those were 8 inches tall and 3 inches in diameter. The switching powersupply made this thing a lighe weight "desktop" freindly unit. you could pick it up and easily move it.

It was partly the use of dynamic memory instead of static memory that made this possible. The power draw on static memory is enourmous. and the memory density on static memory was tiny. plus it was very expensive. it consumed most of the mother board. Today's computers would not be possible without it.

I assumed the apple II was a toy when I saw it's teeny tiny plug-in buss cards. until I looked at it's design. svelt memory mapped cards. all the address space decoding was done by the mother board so you didn't have to waste repetative logic on each card decoding it's own address. same with the power regulation. The switich power supply also gave lower ripple so less regulation was needed.

When apple came out with a disk it was the first reliable soft sectored floppy. I had sold lots of softsectored (8") floppies made by others and saw most of them come back too. Who wants an unrelaible storage system. The apple one worked. and soft secotring made it cheap since it had almost no added electorinics on board. It was all driven from software.

Then of course there was the choice of the 6502. it was a breath fo freshair compared to the 8080. It piplined the next instruction. it used relative jump extensively (calucalting an offset based on a register value not the hardwired instruction). It only had an accumulator and three registers. All the rest were memory mapped to the first 256 bytes of memory. So effectively it had enough registers you could really do something. the 8080 was hamstrung and register bound. and because of the pipelining the 6502 didn't lose any speed for the memory fetch using memory mapped registers.

However even then the MHZ myth was strong. people thought a 4Mhz intel must be faster than a 1Mhz 6502. It was not. nearly all the 8080 instructions were 3 to 5 clock cycles in length