3 ms·

I was speaking with Hermann about this article so asked him and he confirmed what you said: > I do not remember IBM featuring so prominently in our deliberatio

I was speaking with Hermann about this article so asked him and he confirmed what you said: > I do not remember IBM featuring so prominently in our deliberations. Our starting point was a 16 bit version of the 6502.

klelatti 4y ago
I think it might have been Andy Hopper who pushed the RISC papers forward (IBM / Berkeley etc). There is an interesting interview with Hermann where he says that Acorn asked Intel for a special version of the 80286. I've always been puzzled by that given how weak the 286 was!
- HarHarVeryFunny 4y ago
  > There is an interesting interview with Hermann where he says that Acorn asked Intel for a special version of the 80286 First I've heard of that. Did he give any details of what it was being considered for, or what special features were being asked for ?
  - klelatti 4y ago
    Said the team liked it but wanted address and data bus demultiplexed - but the 286 already has demultiplexed buses unlike the 8086. Maybe I misunderstood! It’s here I think: https://m.youtube.com/watch?v=w1HODsDGMzI https://m.youtube.com/watch?v=w1HODsDGMzI
    - HarHarVeryFunny 4y ago
      Thanks. Yeah, that doesn't sound quite right. There must have been some approach to Intel, but that particular complaint applies to the 8086 not the 286. There was certainly a big emphasis on memory bandwidth at Acorn. There's a video by Sophie Wilson (who I knew pre-Sophie - worked with her to reuse BBC BASIC floating point libary for ISO Pascal) describing how Acorn found that, across various process architectures being evaluated, performance was directly related to instruction fetch speed regardless of how that broke down in terms of clock speed, bus width or cycles per instruction. Acorn had of course been experimenting with most of the next-gen processors at the time, and put out a few in "2nd processor" form before a bit later repackaging them as the Acorn Business Computer series. There was actually a prototype 286-based version of the business computer, but by then the ARM was already being developed. I don't recall hearing anything about the 286 being evaluated by Acorn the time (I was there from 82-85). It's interesting that the 286 and Nat Semi 16032 both came out in '82, and Acorn chose to go with the 16032 as a 2nd processor (I still have one - did some work on PANOS) rather than the 286. Perhaps this is the time frame Hermann is talking about? The "If Intel hadn't rejected us, there'd have been no ARM" story it cute to make Intel look foolish, but it's not obvious that a 286 2nd processor would have curtailed ARM development anymore than the 16032 had.
      - klelatti 4y ago
        Thanks so much for coming back. I wondered if I was missing something in what Hermann was saying! It must have been interesting to work with Sophie. I remember looking at some disassembly of the BBC Basic 6502 code and being fascinated by how she got such good performance out of it. Does your 16032 still work? Must be fairly rare if it does! I was at the Uni at the time ARM was launched. Remember going to a University Computer Society meeting where I think (my memory is a bit vague at this point) Steve Furber presented the first Arm. No one could quite believe what they'd done. I'm working on a series of articles for my blog on the early days of RISC. Comparing with the other RISC architectures it's really interesting how they differ. I think Sophie / Steve did a fantastic job of turning RISC into a practical and cost effective reality. I've just had a twitter conversation with Ben Finn (of Sibelius music software fame) who was saying how pleasant writing ARM assembly was!

klelatti 4y ago

I think it might have been Andy Hopper who pushed the RISC papers forward (IBM / Berkeley etc). There is an interesting interview with Hermann where he says that Acorn asked Intel for a special version of the 80286. I've always been puzzled by that given how weak the 286 was!

HarHarVeryFunny 4y ago
> There is an interesting interview with Hermann where he says that Acorn asked Intel for a special version of the 80286 First I've heard of that. Did he give any details of what it was being considered for, or what special features were being asked for ?
- klelatti 4y ago
  Said the team liked it but wanted address and data bus demultiplexed - but the 286 already has demultiplexed buses unlike the 8086. Maybe I misunderstood! It’s here I think: https://m.youtube.com/watch?v=w1HODsDGMzI https://m.youtube.com/watch?v=w1HODsDGMzI
  - HarHarVeryFunny 4y ago
    Thanks. Yeah, that doesn't sound quite right. There must have been some approach to Intel, but that particular complaint applies to the 8086 not the 286. There was certainly a big emphasis on memory bandwidth at Acorn. There's a video by Sophie Wilson (who I knew pre-Sophie - worked with her to reuse BBC BASIC floating point libary for ISO Pascal) describing how Acorn found that, across various process architectures being evaluated, performance was directly related to instruction fetch speed regardless of how that broke down in terms of clock speed, bus width or cycles per instruction. Acorn had of course been experimenting with most of the next-gen processors at the time, and put out a few in "2nd processor" form before a bit later repackaging them as the Acorn Business Computer series. There was actually a prototype 286-based version of the business computer, but by then the ARM was already being developed. I don't recall hearing anything about the 286 being evaluated by Acorn the time (I was there from 82-85). It's interesting that the 286 and Nat Semi 16032 both came out in '82, and Acorn chose to go with the 16032 as a 2nd processor (I still have one - did some work on PANOS) rather than the 286. Perhaps this is the time frame Hermann is talking about? The "If Intel hadn't rejected us, there'd have been no ARM" story it cute to make Intel look foolish, but it's not obvious that a 286 2nd processor would have curtailed ARM development anymore than the 16032 had.
    - klelatti 4y ago
      Thanks so much for coming back. I wondered if I was missing something in what Hermann was saying! It must have been interesting to work with Sophie. I remember looking at some disassembly of the BBC Basic 6502 code and being fascinated by how she got such good performance out of it. Does your 16032 still work? Must be fairly rare if it does! I was at the Uni at the time ARM was launched. Remember going to a University Computer Society meeting where I think (my memory is a bit vague at this point) Steve Furber presented the first Arm. No one could quite believe what they'd done. I'm working on a series of articles for my blog on the early days of RISC. Comparing with the other RISC architectures it's really interesting how they differ. I think Sophie / Steve did a fantastic job of turning RISC into a practical and cost effective reality. I've just had a twitter conversation with Ben Finn (of Sibelius music software fame) who was saying how pleasant writing ARM assembly was!