5 ms·

A history of ARM, part 1: Building the first chip (2022)

118 points by ibobev 1y ago

pinewurst 1y ago
(2022)
philomathdan 1y ago
Part 2: https://arstechnica.com/gadgets/2022/11/a-history-of-arm-part-2-everything-starts-to-come-together/ https://arstechnica.com/gadgets/2022/11/a-history-of-arm-par... Part 3: https://arstechnica.com/gadgets/2023/01/a-history-of-arm-part-3-coming-full-circle/ https://arstechnica.com/gadgets/2023/01/a-history-of-arm-par...
rubatuga 1y ago
Now they are trying to extract every penny from its licensees and competing with their customers.
BallyBrain 1y ago
I love the Acorn story and British computing in general. BBC made a good movie on the subject called Micro Men. Definitely worth a watch despite some inaccuracies. Note that Sophie Wilson was previously known as Roger Wilson and has a cameo at the end of the film.
afandian 1y ago
For anyone interested in this era. I have a couple of sets of RISC OS 2 ROMs chips from 1988 sitting on my desk. I don't know if they still work. If there's a good home in the UK I'd be happy to post them.
- devnullbrain 1y ago
  The Centre for Computing History may be interested
  - afandian 1y ago
    Thanks, I'll get in touch. But I imagine that there are lots of them floating around due to OS upgrades.
ochrist 1y ago
Nice article. Just a couple of comments: Doesn't the x86 chips also use microcode? There are several differences between RISC and CISC not mentioned here. (also Sophie was called Roger at this point in time, so the article has been retconed)
- Symmetry 1y ago
  Yes, the 80286 used microcode and so instruction took several cycles. That's what the article was gesturing at when it said "But another reason was that more complex instructions took longer for a chip to execute. By keeping them simple, you could make every instruction execute in a single clock cycle." EDIT: Though later, in the Pentium era, x86 started to do simple instructions like `ADD AX, [BX]` without microcode.
  - monocasa 1y ago
    Eh, that's just an internal design decision. The ARM1 used microcode as well.
    - jecel 1y ago
      ARM1 had multicycle instructions (LDM and STM) and the ARM2 added more (MUL and MLA) but as far as I know these were controlled by hardwired finite state machines, not microcode.
      - monocasa 1y ago
        https://www.righto.com/2016/02/reverse-engineering-arm1-processors.html https://www.righto.com/2016/02/reverse-engineering-arm1-proc...
        jecel 1y ago
        Thanks for the link. As Ken points out at the end, "Probably the biggest objection to calling the ARM1 microcoded is that the designers of the ARM chip didn't consider it that way.[4] Furber mentions that some commercial RISC processors use microcode, but doesn't apply that term to the ARM1". My opinion is the same as Steve Furber's, though I can certainly see Ken Sherriff's viewpoint. In theory PLAs and ROMs are fully equivalent. In practice, while the ROM can accept any possible "microcode", a PLA might have to be enlarged if you want to change some of the "micro instruction". This need to change the hardware to change the functionality of an instruction is what makes me consider this design hardwired instead of microcoded. [EDIT] Another issue is that the ARM1 has three pipeline stages. The "microcode" here is not used for the fetch and decode stages, only the execute one. So though register to register operations take 3 clock cycles to execute, only one "micro instruction" is needed (the second line in the table).
klelatti 1y ago
May also be of interest on the history of ARM - up to 1997: https://thechipletter.substack.com/p/the-arm-story-part-1-from-acorns-6e2 https://thechipletter.substack.com/p/the-arm-story-part-1-fr... https://thechipletter.substack.com/p/the-arm-story-part-2-archimedes-to-4fd https://thechipletter.substack.com/p/the-arm-story-part-2-ar... https://thechipletter.substack.com/p/the-arm-story-part-3-creating-a-global-1b0 https://thechipletter.substack.com/p/the-arm-story-part-3-cr... This interview with ARM's first CEO Robin Saxby is also really entertaining and informative. His energy is really infectious: https://www.youtube.com/watch?v=FO5PsAY5aaI&t=1823s https://www.youtube.com/watch?v=FO5PsAY5aaI&t=1823s
- fidotron 1y ago
  I think there's a case that Saxby himself was more responsible for ARM's success than the technical merits their early designs may or may not have had. What those early Archimedes systems demonstrated was that the whole thing did actually work, but their design was not what the market needed. Saxby was the right guy to lead them, and his energy just seems like something else. Sophie (a major computing hero for many in the UK in my era) went on to do esoteric VLIW work at Broadcom for ADSL iirc.
  - klelatti 1y ago
    Agree 100%. I think that without Saxby there would be no Arm as we know it today. IIRC Steve Furber and colleagues considered the licensing model and decided it would never work. Saxby made it work. All credit to him too for standing down before he overstayed his welcome and keeping out the limelight since. Yes, re Sophie it was Firepath I think as per this presentation (2014). https://old.hotchips.org/wp-content/uploads/hc_archives/hc14/3_Tue/23_wilson.pdf https://old.hotchips.org/wp-content/uploads/hc_archives/hc14...
nxobject 1y ago
> The ARM chip was also designed to run at very low power. Wilson explained that this was entirely a cost-saving measure—the team wanted to use a plastic case for the chip instead of a ceramic one, so they set a maximum target of 1 watt of power usage. With my (limited) understanding of how ARM conquered the market, I guess this turned out to be a very consequential cost-saving measure.
joz1-k 1y ago
BTW, there are also other interesting, low-power RISC architectures that are used in millions of devices, but most people have never heard of them. For example: * SuperH [0], 32bit only, now basically dead, but microcontrollers are still available * AVR32 [1], 32 bit only, also quite dead * ARC [2], 32/64bit, still quite popular in an automotive [0]: https://en.wikipedia.org/wiki/SuperH https://en.wikipedia.org/wiki/SuperH [1]: https://en.wikipedia.org/wiki/AVR32 https://en.wikipedia.org/wiki/AVR32 [2]: <https://en.wikipedia.org/wiki/ARC_(processor) https://en.wikipedia.org/wiki/ARC_(processor)>
- klelatti 1y ago
  IIRC Arm licensed 'short instruction' encoding from Hitachi where it had been used SuperH to create Thumb which was key in getting Arm into phones.
nasretdinov 1y ago
> In fact, one of the first test boards the team plugged the ARM into had a broken connection and was not attached to any power at all. It was a big surprise when they found the fault because the CPU had been working the whole time. It had turned on just from electrical leakage coming from the support chips. So this not an urban legend after all, and it's about the first ever ARM CPU! Very cool story indeed
- AdamConwayIE 1y ago
  There's even an interview with Steve Furber, who co-designed it, where he talks about it. https://www.youtube.com/watch?v=1jOJl8gRPyQ&t=508s https://www.youtube.com/watch?v=1jOJl8gRPyQ&t=508s
commandersaki 1y ago
The link to the IBM RISC paper didn't seem to work and I'm not sure if this is the paper that they're linking to since it is from 1990, but I found one of IBM's paper on RISC: https://sci-hub.se/10.1147/rd.341.0004 https://sci-hub.se/10.1147/rd.341.0004 What I didn't realise is RISC existed and was an initiative by IBM prior to Dave Patterson research and coining of the term.
- iberator 1y ago
  The joke goes something like: "I people programmed RISC in assembly when you were still in kindergarten" haha I remember the quote but not the source :(

118 points by ibobev 1y ago

(2022)

Part 2: https://arstechnica.com/gadgets/2022/11/a-history-of-arm-part-2-everything-starts-to-come-together/ https://arstechnica.com/gadgets/2022/11/a-history-of-arm-par... Part 3: https://arstechnica.com/gadgets/2023/01/a-history-of-arm-part-3-coming-full-circle/ https://arstechnica.com/gadgets/2023/01/a-history-of-arm-par...

rubatuga 1y ago

Now they are trying to extract every penny from its licensees and competing with their customers.

BallyBrain 1y ago

I love the Acorn story and British computing in general. BBC made a good movie on the subject called Micro Men. Definitely worth a watch despite some inaccuracies. Note that Sophie Wilson was previously known as Roger Wilson and has a cameo at the end of the film.

afandian 1y ago

For anyone interested in this era. I have a couple of sets of RISC OS 2 ROMs chips from 1988 sitting on my desk. I don't know if they still work. If there's a good home in the UK I'd be happy to post them.

devnullbrain 1y ago
The Centre for Computing History may be interested
- afandian 1y ago
  Thanks, I'll get in touch. But I imagine that there are lots of them floating around due to OS upgrades.

ochrist 1y ago

Nice article. Just a couple of comments: Doesn't the x86 chips also use microcode? There are several differences between RISC and CISC not mentioned here. (also Sophie was called Roger at this point in time, so the article has been retconed)

Symmetry 1y ago
Yes, the 80286 used microcode and so instruction took several cycles. That's what the article was gesturing at when it said "But another reason was that more complex instructions took longer for a chip to execute. By keeping them simple, you could make every instruction execute in a single clock cycle." EDIT: Though later, in the Pentium era, x86 started to do simple instructions like `ADD AX, [BX]` without microcode.
- monocasa 1y ago
  Eh, that's just an internal design decision. The ARM1 used microcode as well.
  - jecel 1y ago
    ARM1 had multicycle instructions (LDM and STM) and the ARM2 added more (MUL and MLA) but as far as I know these were controlled by hardwired finite state machines, not microcode.
    - monocasa 1y ago
      https://www.righto.com/2016/02/reverse-engineering-arm1-processors.html https://www.righto.com/2016/02/reverse-engineering-arm1-proc...
      - jecel 1y ago
        Thanks for the link. As Ken points out at the end, "Probably the biggest objection to calling the ARM1 microcoded is that the designers of the ARM chip didn't consider it that way.[4] Furber mentions that some commercial RISC processors use microcode, but doesn't apply that term to the ARM1". My opinion is the same as Steve Furber's, though I can certainly see Ken Sherriff's viewpoint. In theory PLAs and ROMs are fully equivalent. In practice, while the ROM can accept any possible "microcode", a PLA might have to be enlarged if you want to change some of the "micro instruction". This need to change the hardware to change the functionality of an instruction is what makes me consider this design hardwired instead of microcoded. [EDIT] Another issue is that the ARM1 has three pipeline stages. The "microcode" here is not used for the fetch and decode stages, only the execute one. So though register to register operations take 3 clock cycles to execute, only one "micro instruction" is needed (the second line in the table).

klelatti 1y ago

May also be of interest on the history of ARM - up to 1997: https://thechipletter.substack.com/p/the-arm-story-part-1-from-acorns-6e2 https://thechipletter.substack.com/p/the-arm-story-part-1-fr... https://thechipletter.substack.com/p/the-arm-story-part-2-archimedes-to-4fd https://thechipletter.substack.com/p/the-arm-story-part-2-ar... https://thechipletter.substack.com/p/the-arm-story-part-3-creating-a-global-1b0 https://thechipletter.substack.com/p/the-arm-story-part-3-cr... This interview with ARM's first CEO Robin Saxby is also really entertaining and informative. His energy is really infectious: https://www.youtube.com/watch?v=FO5PsAY5aaI&t=1823s https://www.youtube.com/watch?v=FO5PsAY5aaI&t=1823s

fidotron 1y ago
I think there's a case that Saxby himself was more responsible for ARM's success than the technical merits their early designs may or may not have had. What those early Archimedes systems demonstrated was that the whole thing did actually work, but their design was not what the market needed. Saxby was the right guy to lead them, and his energy just seems like something else. Sophie (a major computing hero for many in the UK in my era) went on to do esoteric VLIW work at Broadcom for ADSL iirc.
- klelatti 1y ago
  Agree 100%. I think that without Saxby there would be no Arm as we know it today. IIRC Steve Furber and colleagues considered the licensing model and decided it would never work. Saxby made it work. All credit to him too for standing down before he overstayed his welcome and keeping out the limelight since. Yes, re Sophie it was Firepath I think as per this presentation (2014). https://old.hotchips.org/wp-content/uploads/hc_archives/hc14/3_Tue/23_wilson.pdf https://old.hotchips.org/wp-content/uploads/hc_archives/hc14...

nxobject 1y ago

> The ARM chip was also designed to run at very low power. Wilson explained that this was entirely a cost-saving measure—the team wanted to use a plastic case for the chip instead of a ceramic one, so they set a maximum target of 1 watt of power usage. With my (limited) understanding of how ARM conquered the market, I guess this turned out to be a very consequential cost-saving measure.

joz1-k 1y ago

BTW, there are also other interesting, low-power RISC architectures that are used in millions of devices, but most people have never heard of them. For example: * SuperH [0], 32bit only, now basically dead, but microcontrollers are still available * AVR32 [1], 32 bit only, also quite dead * ARC [2], 32/64bit, still quite popular in an automotive [0]: https://en.wikipedia.org/wiki/SuperH https://en.wikipedia.org/wiki/SuperH [1]: https://en.wikipedia.org/wiki/AVR32 https://en.wikipedia.org/wiki/AVR32 [2]: <https://en.wikipedia.org/wiki/ARC_(processor) https://en.wikipedia.org/wiki/ARC_(processor)>

klelatti 1y ago
IIRC Arm licensed 'short instruction' encoding from Hitachi where it had been used SuperH to create Thumb which was key in getting Arm into phones.

nasretdinov 1y ago

> In fact, one of the first test boards the team plugged the ARM into had a broken connection and was not attached to any power at all. It was a big surprise when they found the fault because the CPU had been working the whole time. It had turned on just from electrical leakage coming from the support chips. So this not an urban legend after all, and it's about the first ever ARM CPU! Very cool story indeed

AdamConwayIE 1y ago
There's even an interview with Steve Furber, who co-designed it, where he talks about it. https://www.youtube.com/watch?v=1jOJl8gRPyQ&t=508s https://www.youtube.com/watch?v=1jOJl8gRPyQ&t=508s

commandersaki 1y ago

The link to the IBM RISC paper didn't seem to work and I'm not sure if this is the paper that they're linking to since it is from 1990, but I found one of IBM's paper on RISC: https://sci-hub.se/10.1147/rd.341.0004 https://sci-hub.se/10.1147/rd.341.0004 What I didn't realise is RISC existed and was an initiative by IBM prior to Dave Patterson research and coining of the term.

iberator 1y ago
The joke goes something like: "I people programmed RISC in assembly when you were still in kindergarten" haha I remember the quote but not the source :(