The first design with the first question

While writing the sequel to Gates, Volts... I've reached the point where it's time to do the first construction. So I thought I'd post the instructions as a sort of taster and teaser, so you know what to look forward to.

The first build will be a very minimal computer: processor, memory and peripheral circuitry.

At first I thought it's pretty obvious, it's going to be a Z80, 8255 for parallel ports, 8251 for terminal communication, 32k ROM and 32k RAM. That's five chips, plus glue logic, so that's like six, seven chips total.

But then I thought: Everybody here knows the Z80, how about something exotic? Well, exotics, as it were: the 6502 was used by Atari and Commodore, and it wasn't as widespread here as Intel, but whatever...

Or if I'm starting ab ovo, how about trying the 8080? Well, I'd rather not, I'd scare people away. What about the 8085? One single support circuit... The advantage would be that PMD owners would feel "at home".

Or maybe something from Motorola? I guess the 6800 isn't very promising anymore, but the 6809 is a safe bet! The best 8-bit processor (quite seriously) of the time...

So I let the vote go. On FB it only goes with two variants unfortunately, there the Z80 wins over the 6502. On Twitter there is a hot battle between the Z80 and the 8085 and so far Intel wins, but it's very close. Motorola is somewhere in the middle of the field and the 6502 limps all the way to the back.

All right, folks, I'll give it to you: The design with the Z80 is pretty lackluster. I plan to use the Z80 in one very nice design where you create maximum effect with minimum components, including running CP/M, but more on that later.

I would like a design with a 6502 or 8085. Those are processors half a generation older and simpler than the other two. The 6502 would be nice to remind local readers, because it's a bit of a different world than Intel, and it's true that as many processor architectures as you know, you're a system programmer! The 8085 would again be a complete Czech classic, and I guess it would be the second design with this processor after the BOB85...

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Martin Maly

Martin Maly

Programmer, journalist, writer and electronic hobbyist. Vintage CPU lover. Creating new computers with the spirit of 80's.