Eight More '8-Bit Era' Microprocessors • Hacker News Board

Re: Eight More '8-Bit Era' Microprocessors

#21

Post by shrubble » Mon, May 11, 2026, 5:41 AM UTC

repelsteeltje wrote: post #2

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.

It depends on how you want to treat the internal (not seen by user or compiler) decoding that both AMD and Intel are doing; some would argue that these CPUs are RISC chips that decode x86 and x64 instructions into their own RISC implementation.

Re: Eight More '8-Bit Era' Microprocessors

#22

Post by anthk » Mon, May 11, 2026, 6:21 AM UTC

The 6809 was a little of a beast too. It powered the Vectrex and some TRS-80 Color models.

The OS was interesting too: https://en.wikipedia.org/wiki/OS-9

Re: Eight More '8-Bit Era' Microprocessors

#23

Post by duskwuff » Mon, May 11, 2026, 6:29 AM UTC

nicole_express wrote: post #10

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 comm…

Given the era, I wouldn't be surprised if it came down to "someone on the development team liked that part". (Or "someone in the purchasing department got a bunch of them really cheap".)

Re: Eight More '8-Bit Era' Microprocessors

#24

Post by adrian_b » Mon, May 11, 2026, 7:00 AM UTC

jecel wrote: post #19

watersb wrote: post #4

Earlier quoted context omitted.

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.

I think there were actually 68000 transistor positions. In the ROMs and PLAs not every potential transistor is populated but the missing ones were counted as well. But the number of actual transistors is only slightly smaller so it doesn't really matter.

I do not remember the exact number of transistors in MC 68000, but I think that it was less than 40000, so not just slightly smaller. In any case, it had more than twice as many transistors as Zilog Z8000, which was super-optimized for size (a very bad decision of Zilog, which lead to a too long time-to-market and to many initial bugs), and slightly more than 4/3 times as many transistors as Intel 8086.

The 68000 transistors number claimed by the Motorola marketing was close to what you get by dividing the die area to the area of one transistor, so it did not correspond to actual transistor positions.

The MC68000 die had large areas occupied with microprogram ROMs, and there as you say only a part of the array of transistors are active, depending on the stored bits. Nonetheless, a significant part of the die was occupied with random logic, where all the physical transistors are used and a part of the area does not have any transistors.

Re: Eight More '8-Bit Era' Microprocessors

#25

Post by adrian_b » Mon, May 11, 2026, 7:15 AM UTC

ido wrote: post #3

repelsteeltje wrote: post #2

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.

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

The 8-bit monolithic CPUs of the seventies all had a few thousands transistors.

The first generation of true 16-bit CPUs, i.e. Intel 8086, Motorola MC68000 and Zilog Z8000, had almost an order of magnitude more transistors, i.e. in the range of 15000 transistors to 50000 transistors.

The first true 32-bit CPUs, like the National 32000 series, Motorola MC68020 and Intel 80386, had a few hundred thousand transistors.

By the end of the eighties, the second generation of 32-bit CPUs reached 1 million transistors.

Re: Eight More '8-Bit Era' Microprocessors

#26

Post by fjfaase » Mon, May 11, 2026, 9:12 AM UTC

Question: I once heard somebody talk about a micro-controller (with a minimal instruction set) where every register could be the program counter. It did not have jump or call instructions. You had 'emulate' those with the instruction (possibly conditionally) that changed the assignment of the program counter to one of the instructions. If I am not mistaken, it had eight registers. Does this ring a bell?

Re: Eight More '8-Bit Era' Microprocessors

#27

Post by fjfaase » Mon, May 11, 2026, 9:16 AM UTC

fjfaase wrote: post #26

Question: I once heard somebody talk about a micro-controller (with a minimal instruction set) where every register could be the program counter. It did not have jump or call instructions. You had 'emulate' those with the instruction (possibly conditionally) that changed the assignment of the program counter to one of the instructions. If I am not mistaken, it had eight registers. Does this ring a bell?

This might have been the PDP-11.

Re: Eight More '8-Bit Era' Microprocessors

#28

Post by pjc50 » Mon, May 11, 2026, 9:26 AM UTC

troad wrote: post #17

Slightly orthogonal, but I'm curious how much effort is going into capturing historic hardware in accurate FPGA representation? There'll come a day when the final physical 6502, 80486 (etc etc) powers off for the final time, and it seems like these technologies would be worth preserving. (I'm sure this is much easier said than done, not trying to minimise the effort involved.) Is there a project that does something l…

The 6502 is one of the most heavily preserved technologies: http://www.visual6502.org/JSSim/index.html

Full die capture, full transistor level simulation.

Most of the others are being emulated in proportion to their importance to games, in arcade machines and consoles. Those emulations are going to be as cycle-accurate as required.

There are some issues around things like the Yamaha synth chips, which are mixed-signal and depend on analogue properties that can be difficult to emulate.

Re: Eight More '8-Bit Era' Microprocessors

#29

Post by pjc50 » Mon, May 11, 2026, 9:29 AM UTC

repelsteeltje wrote: post #2

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.

> ISAs other than x86 (spec. RISC designs) would win in the end

They're correct: ARM won the mobile space, won Apple, and is very gradually seeping into wider availability for other operating systems.

Never mind the majority of raw FLOPS these days are almost certainly going through GPU architectures.

Re: Eight More '8-Bit Era' Microprocessors

#30

Post by drmpeg » Mon, May 11, 2026, 9:42 AM UTC

The article kind of disses the Intel 8085. For those of us with 8080 code bases that were never going to be rewritten for the Z80, it was a welcome upgrade. On the paper dryer process control systems I was working on in 1979, the 8085 based Intel 80/30 Multibus SBC could be dropped in for the older 8080 based 80/20 SBC with no changes and provide a significant 2.5X performance upgrade.