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Bringing Back the PDP8
Anne Thwacks writes " Andrew Grillet has decided that the Digial PDP8 - the first ever minicomputer, will rise from the dead.
He is calling it the PDQ8. Sure others have done software emulations, and even hardware clones, but he is not just building a hardware clone, but trying to revive the whole idea of 12 bit computers!"
while the geek factor may be high, what sort of 12-bit software is it going to run ? linux?
An idea whose time has passed. Maybe he can build an Edsel while he is at it.
If you aren't part of the solution, there is good money to be made prolonging the problem
It would be fun to play around with something cool like that, just for the sheer ability to say "Hey, y'all watch this!" (Oops, better watch that there accent, ya rekcon?) It would especially nice to have a C compiler or something to develop apps for it, again just for the coolness factor.
With a twelve-bit computer, what is the address space, anyway? Something like 2048 words? Suprisingly, you can actually do a lot with that if you code it tightly. No, can't do weather map rendering too well or anything like that, but I bet you could pull off a stripped down version of NetHack or something...
Coolness, regardless. :-)
Be excellent to each other. And... PARTY ON, DUDES!
Some mentioned earlier on this thread jokingly about making a super fast computer based on old architecture.
Has anyone actually done that? Has anyone actually taken say, a Tandy Color Computer 3's hardware and boosted it up to something approaching our current standards? I'm not talking emulation on a x86 platform. I mean fully working with a processor with a native OS.
Those architecture are so simple, with kernels so small you could print the hex binary out on a couple of pages. Imaging how fast an accounting package would be on a 1 gHz, or even a 200 mHz.
I know this maybe off topic, but if someone could resurrect a 12-bit system to a more modern standard, why not other system. DOS is still viable in certain circumstances, why not these platforms.
Think about an 8-bit controller with a serial connection, flash memory, and a RCA video out jack that is based on a C64. There is a TON of documentation for programming on something like that. Linux guruâ(TM)s could use C/C++ and Windows users could use Commodore BASIC.
Oh well thatâ(TM)s just my ramblings.
You say things that offend me and I can deal with it. Can you?
If C is "high-level assembly language," then the PDP-11 is "a computer that directly implements C."
... the PDP-8 still serves as a great example of minimalist design in an era where each bit of the accumulator was implemented by a double-width card (each BIT, thirteen of these cards in all, 12 for the accumulator bits and one for the overflow LINK bit).
Actually it's fair to say that C was developed as a "high level assembly language" for the PDP-11, in other words you've got it slightly backwards. The postfix "++" and prefix "--" operators correspond to the PDP-11's autoindexing mode and when applied to a dereferenced pointer map directly to "(Rn)++" (once the pointer's been moved to a register.
I doubt C would have these constructs if the PDP-11 didn't provide the corresponding register mode.
As far as the PDP-8 being perhaps the most core-efficient design ever, speaking as someone who once developed system software for the PDP-8 and afterwards compilers for the PDP-11, yes, I'd say you're right.
As long as you could fit program and data into 4096 12 bits words, that is. If your program could fit into 4096 12 bit words accessing data in the remaining 28KW was relatively easy due to the semantics of the CDF instruction. But once your code itself outgrew the first 4096 words things got bad in a hurry, because cross-bank subroutine calls using the CIF instruction were fairly expensive.
Gordon Bell designed both the PDP-8 and the PDP-11, and they were designed with different goals in mind. The PDP-8 was designed to be programmed in assembly code - the page and memory bank addressing structure made the development of efficient compilers impossible (it's not an accident that no system programming language like C was never implemented for the PDP-8 architecture).
The PDP-11, on the other hand, was the first minicomputer designed with the compiler writer in mind. The instruction set was very easy to generate code for, much easier than for many mainframe machines that in those days still often had a single accumulator and some auxillary special-purpose registers. The PDP-11's clean, general-purpose register design and (relatively) orthogonal instruction set made compiler writers like myself almost faint in anticipitory pleasure when the design was first announced.
While Gordon Bell designed the PDP-8 and PDP-11, the original engineering plans for the PDP-8 are signed by DeCastro, who did the implementation. He submitted a rival design for DEC's 16 bit minicomputer that was no where near as clean or compiler-writer-friendly as Bell's PDP-11 design.
When the PDP-11 design was chosen, DeCastro left and started Data General, and his 16-bit design became the oft-loathed Nova.
CDC's 12-bit PIC design was much inferior to the PDP-8's, IMO
This DOES make a difference. More important than the space savings is the ability to know that a pattern of bits could not encode any illegal instructions that had to be tested for.