4 ms·

For me the it's disappointing how small a step forward the 8088 was from the Z80 given the increase in the number of transistors. It came a few years later but

For me the it's disappointing how small a step forward the 8088 was from the Z80 given the increase in the number of transistors. It came a few years later but the ARM1 which used 25,000 transistors and was built on roughly the same process size [1] and was much faster than the 8086/8088 shows what might have been had Intel gone down a RISC route. [1] https://en.wikichip.org/wiki/acorn/microarchitectures/arm1 https://en.wikichip.org/wiki/acorn/microarchitectures/arm1

jhallenworld 6y ago
I think you needed cheaper RAM also to enable RISC. At the very least, a 32-bit wide interface was not going to fly this early.
- klelatti 6y ago
  You're absolutely right: ARM1 code density would have been much, much worse than 8088 (which Thumb partly solved later on) and the 32 bit bus wouldn't have been practical. Edit: By complete coincidence browsing some related Z80 came across your memcpy comparison which is fascinating. The step up to the ARM1 is remarkable. I think I remember Herman Hauser saying that Acorn approached Intel for an x86 chip with higher memory bandwidth but were rebuffed and that led to the development of Arm.
  - deleted 6y ago
    [deleted]
justin66 6y ago
> It came a few years later but the ARM1 which used 25,000 transistors and was built on roughly the same process size [1] and was much faster than the 8086/8088 shows what might have been had Intel gone down a RISC route. The 8086 the 8088 was based on was released in 1978. The ARM1 was released in 1985. That was an eternity.
- klelatti 6y ago
  It was a long time but the ARM1 didn't benefit because of the development of Moore's law over that period - if you look at the process, die size and clock speed it's all comparable with the 8086 - the ARM1 was built with very mature (and cheap) technology. As has been said elsewhere the ARM1 wouldn't have worked commercially in 1978 because of code density and bus width.
  - justin66 6y ago
    Well, okay, but it seems more significant to me that the ARM1 did not exist in the late seventies - which would have been really great - because the field advanced. The original comment struck me as a bit strange because it implies that Intel just made a single bad call, or something.
    - klelatti 6y ago
      Very much agree - I was (not very effectively) trying to make the point that its not just about transistor counts and that what you do with those transistors - the field advancing as you say - matters a lot too. Credit to Hennessey etc who developed the original RISC concept. I do think though that if you look back at the history Intel put huge resources into the iAPX432 which was hugely overambitious and they had to rely on the fallback of the 8086/88. There is probably a reasonable case that if they had hadn't split their resources we might have had something better than the 8086.
SomeoneFromCA 6y ago
The King of the era was 68000. 1979. Way ahead of time, comparable to 80286 in many ways, or even 386.
- ncmncm 6y ago
  According to Sophie Wilson, the reason Acorn had to design ARM was that the 8086 and 68000, with no cache, were limited by their bus bandwidth, and so weren't really faster than a contemporaneous 6502; their only real advantage over it was a bigger address range. She is in a position to know.
  - klelatti 6y ago
    Steve Furber has said the same thing and Herman Hauser has said they approached Intel for an 8086 with higher bus bandwidth, but were turned away!
  - SomeoneFromCA 6y ago
    There was no ARM in 1979. At the time ARM came into existence, there were already much faster 68010-68020. The biggest advantage of 68000 is much nicer ISA. 6502 was fast in case of making simple integer computation; for math is was really bad.
    - klelatti 6y ago
      I think it's fair to say when the Acorn team were considering what to replace the 6502 with the chips they compared with were the 68000, 32016 and 80286 - and they felt in each case that memory bandwidth was the constraining factor. In the end the Arm1 with 29,000 transistors had performance that was as good as or exceeded the 68020 with 200,000. Incidentally, Robin Saxby the first CEO of Arm previously worked for Motorola and tried to sell the 68000 to the Acorn team!

jhallenworld 6y ago

I think you needed cheaper RAM also to enable RISC. At the very least, a 32-bit wide interface was not going to fly this early.

klelatti 6y ago
You're absolutely right: ARM1 code density would have been much, much worse than 8088 (which Thumb partly solved later on) and the 32 bit bus wouldn't have been practical. Edit: By complete coincidence browsing some related Z80 came across your memcpy comparison which is fascinating. The step up to the ARM1 is remarkable. I think I remember Herman Hauser saying that Acorn approached Intel for an x86 chip with higher memory bandwidth but were rebuffed and that led to the development of Arm.
- deleted 6y ago
  [deleted]

justin66 6y ago

> It came a few years later but the ARM1 which used 25,000 transistors and was built on roughly the same process size [1] and was much faster than the 8086/8088 shows what might have been had Intel gone down a RISC route. The 8086 the 8088 was based on was released in 1978. The ARM1 was released in 1985. That was an eternity.

klelatti 6y ago
It was a long time but the ARM1 didn't benefit because of the development of Moore's law over that period - if you look at the process, die size and clock speed it's all comparable with the 8086 - the ARM1 was built with very mature (and cheap) technology. As has been said elsewhere the ARM1 wouldn't have worked commercially in 1978 because of code density and bus width.
- justin66 6y ago
  Well, okay, but it seems more significant to me that the ARM1 did not exist in the late seventies - which would have been really great - because the field advanced. The original comment struck me as a bit strange because it implies that Intel just made a single bad call, or something.
  - klelatti 6y ago
    Very much agree - I was (not very effectively) trying to make the point that its not just about transistor counts and that what you do with those transistors - the field advancing as you say - matters a lot too. Credit to Hennessey etc who developed the original RISC concept. I do think though that if you look back at the history Intel put huge resources into the iAPX432 which was hugely overambitious and they had to rely on the fallback of the 8086/88. There is probably a reasonable case that if they had hadn't split their resources we might have had something better than the 8086.

SomeoneFromCA 6y ago

The King of the era was 68000. 1979. Way ahead of time, comparable to 80286 in many ways, or even 386.

ncmncm 6y ago
According to Sophie Wilson, the reason Acorn had to design ARM was that the 8086 and 68000, with no cache, were limited by their bus bandwidth, and so weren't really faster than a contemporaneous 6502; their only real advantage over it was a bigger address range. She is in a position to know.
- klelatti 6y ago
  Steve Furber has said the same thing and Herman Hauser has said they approached Intel for an 8086 with higher bus bandwidth, but were turned away!
- SomeoneFromCA 6y ago
  There was no ARM in 1979. At the time ARM came into existence, there were already much faster 68010-68020. The biggest advantage of 68000 is much nicer ISA. 6502 was fast in case of making simple integer computation; for math is was really bad.
  - klelatti 6y ago
    I think it's fair to say when the Acorn team were considering what to replace the 6502 with the chips they compared with were the 68000, 32016 and 80286 - and they felt in each case that memory bandwidth was the constraining factor. In the end the Arm1 with 29,000 transistors had performance that was as good as or exceeded the 68020 with 200,000. Incidentally, Robin Saxby the first CEO of Arm previously worked for Motorola and tried to sell the 68000 to the Acorn team!