4 ms·

OpenBSD on Motorola 88000 Processors

156 points by rbanffy 8mo ago

readitalready 8mo ago
I still have some of the 88000 reference manuals, and it was really my first introduction to RISC architecture, and I thought it was great. But I never figured out why companies like Apple never chose it for their CPU?
- rbanffy 8mo ago
  The 88000 was implemented across three large ICs. This took an enormous amount of board space and would be unfeasible on the smaller Macs.
- shawn_w 8mo ago
  Complicated, expensive CPU marketed to very high end workstation use? Nobody thought it was worth picking up even if it was faster than the alternatives.
  - hrmtst93837 8mo ago
    [flagged]
    - panick21_ 8mo ago
      Exept of course that Apple internally spent outrages amount of resources on their own CPU project that also wouldnt have had a volume story. Its only because that procet failed that they started looking at alternatives.
- mrpippy 8mo ago
  I believe it was the first RISC that Apple prototyped building a Mac around, including a 68K emulator. IIRC from Gary Davidian’s CHM oral history, it was corporate dealmaking that led to AIM and PPC more than any technical negatives for the 88K. https://computerhistory.org/blog/transplanting-the-macs-central-processor-gary-davidian-and-his-68000-emulator/ https://computerhistory.org/blog/transplanting-the-macs-cent...
  - klodolph 8mo ago
    Yeah, this is probably closest to the right answer. Apple DID choose the 88K, and then changed. Reportedly they put some 88K systems in a Mac chassis. I do wonder what the exact reasons were. Maybe the PPC (complete systems) could be made cheaper? Maybe Apple was worried about relying on a single vendor? I am kind of skeptical of the “corporate dealmaking” angle, because it seems like there are valid technical reasons to NOT choose the 88K. Namely, that it requires companion chips, and the whole system (board + chips) ends up being complicated and expensive.
    - kalleboo 8mo ago
      What I always read was that Apple did not want to be stuck relying only on Motorola again like they were with the 680x0. And it worked out, kinda, Apple had IBM to rely on to make the G5 (until IBM also lost interest) I remember reading that the successor 88110 design with the support chips integrated was announced mainly to woo Apple but I don't know how true that is.
      - fredoralive 8mo ago
        Bitsavers have some documents about the Jaguar RISC project[1] that do indicate Apple's feedback went into the 88110, for example in the System ERS it states "The main processor for the Jaguar is a new version of the Motorola 88000 family which has been enhanced (with input from Jaguar's team) in several areas over the existing implementation. This processor (which will be the MC88110) will be referred to as XJS in the ERS.". There's also an architecture document describing changes Apple wants to make to the 88000 ISA, although I'm not sure how much of this actually got through into the final 88110 (Apple wanted to break binary compatibility, not sure if that happened). [1] The high end RISC machine project that went nowhere, which AFAIK became known as Tesseract when switched to PPC before it fizzled out.
- kev009 8mo ago
  Timing. The 68k still had legs, i.e. the 68040 provided great drop in performance and had an enormous ecosystem and economies of scale. By the time the RISC wars were starting to get fever pitched, the POWER architecture and AIM alliance seemed like a blessing to combine ecosystems and economies of scale for the A and M constituents. And it was.. successful product lines for 2-3 decades from all sorts of embedded systems to G5 workstations to spacecraft.
- cmrdporcupine 8mo ago
  Both Apple and NeXT had machines prototyped around it, but it was initially very expensive I believe, and I think Apple was easily convinced to go with PowerPC ... and rather than evolve it and push it further Motorola dropped it in favour of going in on PowerPC. The sad thing is Intel showed there was still life left in CISC, and Motorola themselves ended up circling back on 68k in the form of ColdFire which proved you could do for 68k what Intel did w/ the Pentium. But by then all their 68k customers had moved on from the 68k ISA.
  - p_l 8mo ago
    68k was much harder to optimize than x86, being way more CISC-y 68k like VAX was seen as dead avenue not only compared to RISC
    - Someone 8mo ago
      > 68k was much harder to optimize than x86 Harder to optimize or because of its orthogonal instruction set easier to write code for?
      - rjsw 8mo ago
        What matters is how easy it is to create an out-of-order implementation of an ISA, there isn't a 680x0 equivalent of the Pentium Pro.
        wk_end 8mo ago
        Well, there's the 68080 - the modern FPGA-based 68k chip designed as an upgrade for Amigas - but that did arrive quite a bit too late. http://www.apollo-core.com/index.htm?page=features http://www.apollo-core.com/index.htm?page=features
        cmrdporcupine 8mo ago
        ColdFire was/is literally that is my understanding. But there was really no market for it. They produced variants up to 300mhz if I recall but then relegated it mostly just to microcontroller market and then stopped developing it. It was too late, and just oh-so-slightly incompatible with 680x0. But I suspect if the ISA used in ColdFire v4 had existed in 1994, 1995 that perhaps Apple's honestly disastrous foray through PowerPC could have been avoided.
- panick21_ 8mo ago
  They did basically. What happened is that Apple own CPU project crashed and burned. Then they had some meetings with people including DEC for Alpha and IBM. IBM offered POWER and IBM was also willing to go in on some other projects, like the next gen OS Teligent. But Apple didn't want to drop Motorola fully. So Motorola, Apple and IBM figured out that with some tweaks to the 88000 the could turn it into something POWER like. And that thing was PowerPC that Motorola supplied to Apple. That's my understanding.
zdw 8mo ago
The 88k multi-chip cache/MMU architecture is fascinating, especially how it could be designed with a single cache chip, or a split I/D cache across two or more different chips.
helf 8mo ago
[dead]
OneDonOne 8mo ago
An excellent source for this architecture is Mitch Alsup and his Usenet posts going back to the late 1980s (he still posted regularly in the 2020s.)
mohite 8mo ago
[flagged]
snvzz 8mo ago
m88k is an ISA primarily designed by Mitch Alsup. Mitch Alsup has extensive experience in ISA design, has participated (tangentially) in informing RISC-V design process. Recently, he's designed my66000, an interesting, fresh take at a new ISA that I recommend exploring.
- Findecanor 8mo ago
  Alsup liked to write a lot about his my66000 on Usenet, but does not share documents about it with everyone. (Yes, I've emailed him and been ignored. I have had to piece together what I know about it from multiple posts.) Apparently it runs in FPGA and there are assemblers and compiler back-ends for it. Like the 88000, the register file is shared between integer and floating point units. One interesting detail is that it supports CRAY-style vector operations using the same architectural registers, and downgrades to scalar operation automatically on interrupts. This means that the register state to load/store on context switches is small.
rbanffy 8mo ago
I confess I have a soft spot for these machines - the road not taken is always tempting to explore. Sadly, it didn't do well on the market, even less in Europe, so there are very few working machines around me and even fewer floating around on eBay. :-(
- pseudohadamard 8mo ago
  I liked the architecture, but my main exposure to it was the DG AvIiIion or however they wanted you to spell it. Chiefly notable for running a Unix, DGUX, that made AIX look good. That takes some doing.
  - rbanffy 8mo ago
    We need better emulators to preserve that. I’ve never experienced DGUX from up close.
    - pseudohadamard 8mo ago
      Oh, it's easy to experience. Go out and buy a pack of 4" nails, then hold them in front of you with the pointy ends towards you and run headlong into a wall or other hard surface. This will give you the DG/UX experience without needing to set up an emulator.
znpy 8mo ago
Weird to see Omron mentioned. I have a digital weight scale from them in my bathroom :)
mrumon 8mo ago
[dead]

156 points by rbanffy 8mo ago

I still have some of the 88000 reference manuals, and it was really my first introduction to RISC architecture, and I thought it was great. But I never figured out why companies like Apple never chose it for their CPU?

rbanffy 8mo ago
The 88000 was implemented across three large ICs. This took an enormous amount of board space and would be unfeasible on the smaller Macs.
shawn_w 8mo ago
Complicated, expensive CPU marketed to very high end workstation use? Nobody thought it was worth picking up even if it was faster than the alternatives.
- hrmtst93837 8mo ago
  [flagged]
  - panick21_ 8mo ago
    Exept of course that Apple internally spent outrages amount of resources on their own CPU project that also wouldnt have had a volume story. Its only because that procet failed that they started looking at alternatives.
mrpippy 8mo ago
I believe it was the first RISC that Apple prototyped building a Mac around, including a 68K emulator. IIRC from Gary Davidian’s CHM oral history, it was corporate dealmaking that led to AIM and PPC more than any technical negatives for the 88K. https://computerhistory.org/blog/transplanting-the-macs-central-processor-gary-davidian-and-his-68000-emulator/ https://computerhistory.org/blog/transplanting-the-macs-cent...
- klodolph 8mo ago
  Yeah, this is probably closest to the right answer. Apple DID choose the 88K, and then changed. Reportedly they put some 88K systems in a Mac chassis. I do wonder what the exact reasons were. Maybe the PPC (complete systems) could be made cheaper? Maybe Apple was worried about relying on a single vendor? I am kind of skeptical of the “corporate dealmaking” angle, because it seems like there are valid technical reasons to NOT choose the 88K. Namely, that it requires companion chips, and the whole system (board + chips) ends up being complicated and expensive.
  - kalleboo 8mo ago
    What I always read was that Apple did not want to be stuck relying only on Motorola again like they were with the 680x0. And it worked out, kinda, Apple had IBM to rely on to make the G5 (until IBM also lost interest) I remember reading that the successor 88110 design with the support chips integrated was announced mainly to woo Apple but I don't know how true that is.
    - fredoralive 8mo ago
      Bitsavers have some documents about the Jaguar RISC project[1] that do indicate Apple's feedback went into the 88110, for example in the System ERS it states "The main processor for the Jaguar is a new version of the Motorola 88000 family which has been enhanced (with input from Jaguar's team) in several areas over the existing implementation. This processor (which will be the MC88110) will be referred to as XJS in the ERS.". There's also an architecture document describing changes Apple wants to make to the 88000 ISA, although I'm not sure how much of this actually got through into the final 88110 (Apple wanted to break binary compatibility, not sure if that happened). [1] The high end RISC machine project that went nowhere, which AFAIK became known as Tesseract when switched to PPC before it fizzled out.
kev009 8mo ago
Timing. The 68k still had legs, i.e. the 68040 provided great drop in performance and had an enormous ecosystem and economies of scale. By the time the RISC wars were starting to get fever pitched, the POWER architecture and AIM alliance seemed like a blessing to combine ecosystems and economies of scale for the A and M constituents. And it was.. successful product lines for 2-3 decades from all sorts of embedded systems to G5 workstations to spacecraft.
cmrdporcupine 8mo ago
Both Apple and NeXT had machines prototyped around it, but it was initially very expensive I believe, and I think Apple was easily convinced to go with PowerPC ... and rather than evolve it and push it further Motorola dropped it in favour of going in on PowerPC. The sad thing is Intel showed there was still life left in CISC, and Motorola themselves ended up circling back on 68k in the form of ColdFire which proved you could do for 68k what Intel did w/ the Pentium. But by then all their 68k customers had moved on from the 68k ISA.
- p_l 8mo ago
  68k was much harder to optimize than x86, being way more CISC-y 68k like VAX was seen as dead avenue not only compared to RISC
  - Someone 8mo ago
    > 68k was much harder to optimize than x86 Harder to optimize or because of its orthogonal instruction set easier to write code for?
    - rjsw 8mo ago
      What matters is how easy it is to create an out-of-order implementation of an ISA, there isn't a 680x0 equivalent of the Pentium Pro.
      - wk_end 8mo ago
        Well, there's the 68080 - the modern FPGA-based 68k chip designed as an upgrade for Amigas - but that did arrive quite a bit too late. http://www.apollo-core.com/index.htm?page=features http://www.apollo-core.com/index.htm?page=features
      - cmrdporcupine 8mo ago
        ColdFire was/is literally that is my understanding. But there was really no market for it. They produced variants up to 300mhz if I recall but then relegated it mostly just to microcontroller market and then stopped developing it. It was too late, and just oh-so-slightly incompatible with 680x0. But I suspect if the ISA used in ColdFire v4 had existed in 1994, 1995 that perhaps Apple's honestly disastrous foray through PowerPC could have been avoided.
panick21_ 8mo ago
They did basically. What happened is that Apple own CPU project crashed and burned. Then they had some meetings with people including DEC for Alpha and IBM. IBM offered POWER and IBM was also willing to go in on some other projects, like the next gen OS Teligent. But Apple didn't want to drop Motorola fully. So Motorola, Apple and IBM figured out that with some tweaks to the 88000 the could turn it into something POWER like. And that thing was PowerPC that Motorola supplied to Apple. That's my understanding.

zdw 8mo ago

The 88k multi-chip cache/MMU architecture is fascinating, especially how it could be designed with a single cache chip, or a split I/D cache across two or more different chips.

helf 8mo ago

[dead]

OneDonOne 8mo ago

An excellent source for this architecture is Mitch Alsup and his Usenet posts going back to the late 1980s (he still posted regularly in the 2020s.)

mohite 8mo ago

[flagged]

snvzz 8mo ago

m88k is an ISA primarily designed by Mitch Alsup. Mitch Alsup has extensive experience in ISA design, has participated (tangentially) in informing RISC-V design process. Recently, he's designed my66000, an interesting, fresh take at a new ISA that I recommend exploring.

Findecanor 8mo ago
Alsup liked to write a lot about his my66000 on Usenet, but does not share documents about it with everyone. (Yes, I've emailed him and been ignored. I have had to piece together what I know about it from multiple posts.) Apparently it runs in FPGA and there are assemblers and compiler back-ends for it. Like the 88000, the register file is shared between integer and floating point units. One interesting detail is that it supports CRAY-style vector operations using the same architectural registers, and downgrades to scalar operation automatically on interrupts. This means that the register state to load/store on context switches is small.

rbanffy 8mo ago

I confess I have a soft spot for these machines - the road not taken is always tempting to explore. Sadly, it didn't do well on the market, even less in Europe, so there are very few working machines around me and even fewer floating around on eBay. :-(

pseudohadamard 8mo ago
I liked the architecture, but my main exposure to it was the DG AvIiIion or however they wanted you to spell it. Chiefly notable for running a Unix, DGUX, that made AIX look good. That takes some doing.
- rbanffy 8mo ago
  We need better emulators to preserve that. I’ve never experienced DGUX from up close.
  - pseudohadamard 8mo ago
    Oh, it's easy to experience. Go out and buy a pack of 4" nails, then hold them in front of you with the pointy ends towards you and run headlong into a wall or other hard surface. This will give you the DG/UX experience without needing to set up an emulator.

znpy 8mo ago

Weird to see Omron mentioned. I have a digital weight scale from them in my bathroom :)

mrumon 8mo ago

[dead]