5 ms·

It's an ISA designed last century. It's time to stop tacking on extensions and build something better.

by Two4 2y ago

high_na_euv 2y ago
Name traits that new ISA would need to have that would bring significant improvements
sieabahlpark 2y ago
[dead]
mepian 2y ago
Arm was also designed last century.
- Two4 2y ago
  I'm not criticizing ARM, I'm criticizing x86.
  - foxyv 2y ago
    If you want to criticize x86 then you may want to support the assertion. Maybe something along the lines of bloated legacy features and horrible power requirements. However, in my opinion it's perfectly fine for a desktop computer. Just not so great for phones, tablets and portable computers.
    - shiroiushi 2y ago
      >...horrible power requirements. ... perfectly fine for a desktop computer. Just not so great for phones, tablets and portable computers. Except no one buys desktop computers any more: everyone's using phones, tablets, and laptop computers. There's also servers, but even here power efficiency is important; reduced power requirements for a datacenter would save a lot of money, not just in direct electricity consumption by the servers, but also from reduced cooling needs.
      - high_na_euv 2y ago
        >Except no one buys desktop computers any more Wtf? >Power efficiency Isa has small impact on it.
        dartos 2y ago
        Consumer sales of desktops have been falling for years. A lot of regular office workplaces moved to laptops+docking stations as well. People still buy desktops, but it’s a dying breed outside of gamers artists and those with heavy compute requirements
        shiroiushi 2y ago
        Yeah, and not only that, many of those "desktops" are probably "workstations". We had heavy compute requirements at my last job so we were assigned workstations with dual Xeon CPUs, not standard Intel desktop chips. Outside of a couple unusual places like that, laptops have been the standard for workplaces over the last couple decades for me.
        Tomte 2y ago
        At my employer that started during covid. Before that laptops were not quite limited to managers, but they did signify higher status (if not necessarily pay). Today it‘s iPads that signify status.
        wetpaws 2y ago
        [dead]
      - pjmlp 2y ago
        Ah, that is why Sony and Microsoft are now eyeing PC versions of console games, because no one ever buys gaming rings any longer, aka desktop computers. Also what do you think most contributors to LLVM, GCC, CUDA, VFX,.. use as daily driver?
        2y ago
    - ChocolateGod 2y ago
      > horrible power requirements ISA makes very little difference these days when it comes to power requirements.[1] [1] https://chipsandcheese.com/2021/07/13/arm-or-x86-isa-doesnt-matter/ https://chipsandcheese.com/2021/07/13/arm-or-x86-isa-doesnt-...
      - foxyv 2y ago
        I'm pretty sure that x86 could be more power efficient than it is now. But I have rarely run into an implementation of x86 that wasn't pretty dang power hungry. Probably for the explicit reason that it isn't a huge priority for the stuff they run it on. I think the lowest power ones are Atom and Celeron. All the other low wattage CPUs are RISC based. I think AMD is also coming up with something similar.
        ChocolateGod 2y ago
        Nearly all x86 CPU architectures originate from desktop/server CPUs which had much higher thermal and power limits, but nearly all ARM CPU architectures originate from embedded CPUs where there are strict thermal and power limits. It's not as if there's something fundamental with x86 that makes it use more power. There used to be the case that x86 CPUs had many more transistors (and thus more power usage and heat) due to the need to implement more instructions, but I don't believe this is the case anymore. I think right now is that its easier to scale up an architecture, than it is to scale down. If you look at something like Project Denver, it started as a x86 compatible CPU that would of had ARM-like power usage.
        to11mtm 2y ago
        > I think the lowest power ones are Atom and Celeron. All the other low wattage CPUs are RISC based. I think AMD is also coming up with something similar. AMD Had Bobcat and later Puma, IIRC there were some <5W parts in both of those families. I still wonder -why- they never did a dual channel version of those parts for desktop, my guess is it would have made Bulldozer look extra bad somehow.
  - mepian 2y ago
    I thought we were in the context of the competition between x86 and Arm but sure, what is a non-last century ISA then? RISC-V, a very conservative rehash of an architecture from the 1980s? Realistically there are no other commercially viable contenders, sadly.
  - ffgjgf1 2y ago
    You’re not, though. Or at least didn’t provide a single argument..
- duskwuff 2y ago
  AArch64 was designed in 2011. It's not just A32 with everything widened to 64 bits; it's substantially different.
hulitu 2y ago
You need to port existing programs to your dream arch. It was tried before. With Itanic. /s
- deleted 2y ago
  [deleted]
kbolino 2y ago
Every architecture that survives gets filled with extensions. That's not the issue. Even the time period is not the issue per se, though it plays a part in it. The real dividing line is more like 1985 than 2000 though. CISC is the issue (at least, at the ISA level). Processors of that era were made to be "friendly" to assembly programmers. There are redundant instructions with slightly different semantics, there are many addressing modes, there are not many registers, and the instruction encoding is an illogical variable-length mess hidden away by the assembler. RISC on the other hand starts from the premise that humans don't write assembly much anymore, they write high-level languages (yes even C counts) which get translated into machine code by a compiler. So an ISA is a compiler target first and foremost. So it's better to spend silicon on more registers and more concurrent/parallel work than on addressing modes and convenience instructions. Obviously this battle has already been fought and won on a technical level by RISC; that's what the R in Arm originally stood for, and no modern CPU design even considers CISC. Heck, even x86 uses RISC-like micro-ops under the hood and the 64-bit version of it added a lot more registers. But the CISC instruction decoder is still there taking up some silicon. The real question is: does that extra silicon actually matter that much in practice anymore? It's dwarfed by the other things a modern processor has, especially the cache. The answer seems to be contextual even today. An x86 server, desktop, or gaming console running at or near full load on CPU-intensive tasks still outperforms Arm (though by less and less each year), even though Arm handily takes the crown at lower power levels. Is that due to ISA alone or other factors too?

It's an ISA designed last century. It's time to stop tacking on extensions and build something better.

by Two4 2y ago

It's an ISA designed last century. It's time to stop tacking on extensions and build something better.

high_na_euv 2y ago

Name traits that new ISA would need to have that would bring significant improvements

sieabahlpark 2y ago

[dead]

mepian 2y ago

Arm was also designed last century.

Two4 2y ago
I'm not criticizing ARM, I'm criticizing x86.
- foxyv 2y ago
  If you want to criticize x86 then you may want to support the assertion. Maybe something along the lines of bloated legacy features and horrible power requirements. However, in my opinion it's perfectly fine for a desktop computer. Just not so great for phones, tablets and portable computers.
  - shiroiushi 2y ago
    >...horrible power requirements. ... perfectly fine for a desktop computer. Just not so great for phones, tablets and portable computers. Except no one buys desktop computers any more: everyone's using phones, tablets, and laptop computers. There's also servers, but even here power efficiency is important; reduced power requirements for a datacenter would save a lot of money, not just in direct electricity consumption by the servers, but also from reduced cooling needs.
    - high_na_euv 2y ago
      >Except no one buys desktop computers any more Wtf? >Power efficiency Isa has small impact on it.
      - dartos 2y ago
        Consumer sales of desktops have been falling for years. A lot of regular office workplaces moved to laptops+docking stations as well. People still buy desktops, but it’s a dying breed outside of gamers artists and those with heavy compute requirements
        shiroiushi 2y ago
        Yeah, and not only that, many of those "desktops" are probably "workstations". We had heavy compute requirements at my last job so we were assigned workstations with dual Xeon CPUs, not standard Intel desktop chips. Outside of a couple unusual places like that, laptops have been the standard for workplaces over the last couple decades for me.
        Tomte 2y ago
        At my employer that started during covid. Before that laptops were not quite limited to managers, but they did signify higher status (if not necessarily pay). Today it‘s iPads that signify status.
      - wetpaws 2y ago
        [dead]
    - pjmlp 2y ago
      Ah, that is why Sony and Microsoft are now eyeing PC versions of console games, because no one ever buys gaming rings any longer, aka desktop computers. Also what do you think most contributors to LLVM, GCC, CUDA, VFX,.. use as daily driver?
      - 2y ago
  - ChocolateGod 2y ago
    > horrible power requirements ISA makes very little difference these days when it comes to power requirements.[1] [1] https://chipsandcheese.com/2021/07/13/arm-or-x86-isa-doesnt-matter/ https://chipsandcheese.com/2021/07/13/arm-or-x86-isa-doesnt-...
    - foxyv 2y ago
      I'm pretty sure that x86 could be more power efficient than it is now. But I have rarely run into an implementation of x86 that wasn't pretty dang power hungry. Probably for the explicit reason that it isn't a huge priority for the stuff they run it on. I think the lowest power ones are Atom and Celeron. All the other low wattage CPUs are RISC based. I think AMD is also coming up with something similar.
      - ChocolateGod 2y ago
        Nearly all x86 CPU architectures originate from desktop/server CPUs which had much higher thermal and power limits, but nearly all ARM CPU architectures originate from embedded CPUs where there are strict thermal and power limits. It's not as if there's something fundamental with x86 that makes it use more power. There used to be the case that x86 CPUs had many more transistors (and thus more power usage and heat) due to the need to implement more instructions, but I don't believe this is the case anymore. I think right now is that its easier to scale up an architecture, than it is to scale down. If you look at something like Project Denver, it started as a x86 compatible CPU that would of had ARM-like power usage.
      - to11mtm 2y ago
        > I think the lowest power ones are Atom and Celeron. All the other low wattage CPUs are RISC based. I think AMD is also coming up with something similar. AMD Had Bobcat and later Puma, IIRC there were some <5W parts in both of those families. I still wonder -why- they never did a dual channel version of those parts for desktop, my guess is it would have made Bulldozer look extra bad somehow.
- mepian 2y ago
  I thought we were in the context of the competition between x86 and Arm but sure, what is a non-last century ISA then? RISC-V, a very conservative rehash of an architecture from the 1980s? Realistically there are no other commercially viable contenders, sadly.
- ffgjgf1 2y ago
  You’re not, though. Or at least didn’t provide a single argument..
duskwuff 2y ago
AArch64 was designed in 2011. It's not just A32 with everything widened to 64 bits; it's substantially different.

hulitu 2y ago

You need to port existing programs to your dream arch. It was tried before. With Itanic. /s

deleted 2y ago
[deleted]

kbolino 2y ago

Every architecture that survives gets filled with extensions. That's not the issue. Even the time period is not the issue per se, though it plays a part in it. The real dividing line is more like 1985 than 2000 though. CISC is the issue (at least, at the ISA level). Processors of that era were made to be "friendly" to assembly programmers. There are redundant instructions with slightly different semantics, there are many addressing modes, there are not many registers, and the instruction encoding is an illogical variable-length mess hidden away by the assembler. RISC on the other hand starts from the premise that humans don't write assembly much anymore, they write high-level languages (yes even C counts) which get translated into machine code by a compiler. So an ISA is a compiler target first and foremost. So it's better to spend silicon on more registers and more concurrent/parallel work than on addressing modes and convenience instructions. Obviously this battle has already been fought and won on a technical level by RISC; that's what the R in Arm originally stood for, and no modern CPU design even considers CISC. Heck, even x86 uses RISC-like micro-ops under the hood and the 64-bit version of it added a lot more registers. But the CISC instruction decoder is still there taking up some silicon. The real question is: does that extra silicon actually matter that much in practice anymore? It's dwarfed by the other things a modern processor has, especially the cache. The answer seems to be contextual even today. An x86 server, desktop, or gaming console running at or near full load on CPU-intensive tasks still outperforms Arm (though by less and less each year), even though Arm handily takes the crown at lower power levels. Is that due to ISA alone or other factors too?