Eight More 8-bit Era Microprocessors (2024)

nicole_express•about 1 hour ago

The Signetics 2650 found its way into a bunch of arcade games by lieu of British company Century Electronics. I have a conversion kit of theirs installed into a Donkey Kong Jr. board, which outright replaces DK Jr.'s Z80 with a daughterboard containing the CPU. Always wondered why they chose that in particular, it's not a very common chip, and just using the Z80 that was there and replacing the ROMs was the more common option for conversion kits like that.

classichasclass•about 1 hour ago

Zaccaria pinballs I think used it pretty heavily as well. Again, no clear explanation there either.

drfuchs•about 3 hours ago

I did some assembly programming on the Fairchild F8 mentioned in the prequel article. Quaintest feature: Doing a “long” jump (more than 127 bytes away) would cause the accumulator register to be clobbered. Presumably, there was nowhere else to store the high (low?) order address byte routing things around to the PC register. This was also a problem for the debugger (in ROM on the development system), since continuing from a breakpoint necessitated a long jump, so it couldn’t restore the accumulator. So, the debugger would just simulate instructions until it hit a jump, which it could then jump to. Or something like that. Fairchild provided a listing of the source to the debugger / emulator, and the line that simulated messing up the accumulator during single-stepping was commented “The F8 Touch!” It made an impression 50 years ago.

jhbadger•about 2 hours ago

The RCA-1802 was used in the COSMAC Elf computer which was described as a hobbyist project to build in a series of articles in Popular Electronics 50 years ago. The Elf may be obscure but one thing developed on it (or its successor, the COSMAC VIP), CHIP-8, lives on -- it was (by some definitions) the first "fantasy console" like Pico-8 and TIC-80 today -- a virtual machine designed for writing action games.

https://en.wikipedia.org/wiki/COSMAC_Elf https://en.wikipedia.org/wiki/CHIP-8

heikkilevanto•about 1 hour ago

Oh yes, I cut my teeth on a Finnish 1802 based TELMAC in the 1970s. It all of 2 kb of RAM (in 16 chips manually soldered on the board), and room for another 2kb if anyone would need so much, as it said in the instructions. I might almost be able to reconstruct the instruction set now, it was so deep ingrained in my brain. Once I had nightmares directly in hex. Sold my first pieces of code on that CPU, a 2kb long "monitor" rom, maybe a bit like a BIOS in today's terms. Added .5 kb of new features and optimized it so it could still fit in that 2kb EPROM.

repelsteeltje•2 days ago

It's easy to forget how much innovation divergence was happening in the early 70s. Up till the late nineties we speculated that ISAs other than x86 (spec. RISC designs) would win in the end.

Imagine these 8 bitters were mostly hardwired, with less than a million transistors.

ido•about 3 hours ago

Way less than a million! I believe usually in the order of thousands.

watersb•about 3 hours ago

The Motorola 68000, a great CPU with 32-bit operands, was initially implemented with 68,000 transistors.

The model number was decided long before the transistor-level design was finalized.

vidarh•about 2 hours ago

Indeed. The 6502 had 3510 enhancement transistors and 1018 depletion transistors for a total of 4528...

rzzzt•28 minutes ago

With the layout fitting entirely on a large sheet of paper: https://archive.archaeology.org/1107/features/mos_technology...

userbinator•about 2 hours ago

A 486 already had over a million transistors. These are in the thousands.

Eight More 8-bit Era Microprocessors (2024)

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