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I like the concept, but I'm not sure that the Z-80 is the best implementation substrate -- it's got a lot of oddball properties and special case instruction encodings (due in part to the way things were squeezed in around the base 8080 instruction set).

A PDP-8 can be implemented in fewer transistors (original DEC wiring diagrams are on bitsavers, and github has source for several clones in Verilog), and DEC already shipped a moderately full software suite for it.

I think the point is in that there are so many z80 chips out there for scavenging and that there are plenty of consumer devices that can be used (like TI calculators). Even if they stop making them today, the supply will last long.

They are also the cochroach equivalent of a processor, tough as hell, functional on a ropey power supply and can be used to make a simple 8 bit machine with very few ancillary chips - the reason they ended up in the sinclair zx's.

Similar reasons are likely why they were in the TRS-80.

The TRS-80 was... not built for ruggedness and durability. At least not if you had a system with any peripherals; the cables were notoriously flaky, to the point that the problems are on record in the Wikipedia page, as an explanation for the "Trash-80" sobriquet. (I recall at the time seeing aftermarket recommendations for expensive cables and doing things like wrapping components in tinfoil to try to get some extra RF shielding.)

The system wasn't built for ruggedness. The chip had to be, because the system provided that ropey power supply previously mentioned and very few ancillary chips. It was a relatively inexpensive chip that one could build an even less expensive home computer around.

Precisely this, The ZX80 was a masterpiece of "just how close to the wind can we sail and still have a mostly functional for most people legit computer".

I mean it was built out of off the shelf cheaply (relatively) available TTL components and no real RF shielding (something variants in the US had to fix to comply with the FCC rules of the time).

It's astounding it was a commercial success but it cost 80 quid (as a kit, 100 pre-built) at a time when others where 3-4 to 10 times as expensive (average wage back then was around 110 per week).

In a very real sense it democratised computers to something almost anyone working could afford if they wanted it.

I know if it hadn't of been for the ZX-81/ZX-Spectrum I wouldn't have had a career in software engineering nor a life long love for computers, I was born in '80 to working class parents in the north of England even in 1987 having a computer was considered exotic among my cohort, I didn't see another one outside my family til 1990 (a C64 I lusted after).

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