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Last years Xbox leak revealed that Microsoft was at least considering switching to ARM for the next Xbox generation, though regardless of the CPU architecture t

Last years Xbox leak revealed that Microsoft was at least considering switching to ARM for the next Xbox generation, though regardless of the CPU architecture they chose they indicated they were sticking with AMD for the GPU. It will be interesting to see how that shakes out, going to ARM would complicate backwards compatibility so they would need a very good reason to move.

hypercube33 3y ago
AMD holds an arm license and uses them as part of the software tpu in the pro series processors as I understand. It's not unreasonable to assume they could make some ARM x86 hybrid CPU (like apple did for Rosetta) or a mixed arch chip we've never seen before that can run emulators native. Who knows.
- AnthonyMouse 3y ago
  But what would be the point of that? If you're already buying it from AMD and the previous generation was x86 so that's what gives backwards compatibility, just do another x86 one. The reason to switch to ARM is to get it from someone other than Intel or AMD.
  - lmm 3y ago
    The reason to switch to ARM is to get better performance, especially per-watt. If the supplier that's making your graphics card can deliver that, then why risk onboarding someone new?
    - jwells89 3y ago
      In addition to better perf per watt, it’d allow them to shrink the console, potentially to something as small as a Mac Mini or NUC. Less need for cooling means a smaller console. This could help them make inroads to people who might not have considered a home console before due to their relatively large size. Wouldn’t be surprised if the Switch did well with this market and now MS wants a slice of that pie.
    - isthatafact 3y ago
      > The reason to switch to ARM is to get better performance, especially per-watt. I am not expert, but I cannot remember ever hearing that before. Why would arm have better absolute performance than x86? As a spectator, reading tech press about architectures gave me the impression that even in performance per watt, the advantage arm has over x86 is fairly small, just that arm chip makers have always focused on optimizing for low power performance for phones.
      - lmm 3y ago
        > I am not expert, but I cannot remember ever hearing that before. Why would arm have better absolute performance than x86? Better general design, or easier to include more cache. All the normal reasons one architecture might perform better than another. I mean, you heard about Apple switching all their processors to ARM, right? > As a spectator, reading tech press about architectures gave me the impression that even in performance per watt, the advantage arm has over x86 is fairly small, just that arm chip makers have always focused on optimizing for low power performance for phones. Intel would certainly like you to believe that. But for all their talk of good low-power x86s being possible, no-one's ever actually managed to make one.
        scheeseman486 3y ago
        There's an anecdote from Jim Keller that Zen is so modular that it'd be possible to swap out the x86 instruction decode block with an ARM one with relatively little effort. He's also been saying for a while now that ISA has little bearing on performance and efficiency anymore. Apple's decision to switch to ARM had many reasons, licensing being just as important as performance, perhaps more so. The low power variants of Zen are very efficient. You're still looking at Intel, but they've been leapfrogged by AMD on most fronts over the past half decade (still not market share, but Intel still has their fabrication advantage).
        lmm 3y ago
        I'll believe that when I see a Zen-based phone with a non-awful battery life. Yes AMD are ahead of Intel in some areas, but they've got the same vested interest in talking up how power-efficient their x86 cores can be that may not actually be based in reality.
- mratsim 3y ago
  The stuff on the PRO is a Xilinx FPGA, or they have both an ARM Processor and an FPGA?
  - deleted 3y ago
    [deleted]
  - p_l 3y ago
    The NPUs are effectively hard IP blocks on xilinx FPGA fabric (i.e. there are close to no LUTs there - the chip takes in Xilinx bitstream but the only available resources are hard IP blocks) There's also Xtensa cores (audio coprocessor) and ARM cores included (PSP, Pluton, and I think there's extra ARM coprocessor for handling some sensor stuff optionally)
- bradfa 3y ago
  AMD has previously made a variety of ARM CPUs, such as the recent Opteron “Seattle” parts. https://en.wikichip.org/wiki/amd/cores/seattle https://en.wikichip.org/wiki/amd/cores/seattle
- _kbh_ 3y ago
  > AMD holds an arm license and uses them as part of the software tpu in the pro series processors as I understand. AMD uses ARM for its PSP as well which is more than just a TPM. But afaik it also matters what type of license AMD has. AMD would be need an ARM architecture license (like Apple has). This license allows you to do whatever you want with the chip (such as adding a x86 style memory model). The downside to the architecture license is you have clean room design the chip entirely.
- mkopec 3y ago
  All Zen 1 CPUs and newer have the PSP / ASP security processor which is ARM based and runs before the x86 cores are released from reset. This applies to all Zen models, not just the PRO versions. The fTPM does indeed run on the PSP, so on the ARM cores, among many other things like DRAM training.
dataangel 3y ago
Apple recently demonstrated ARM is pretty capable of emulating x86
- jsheard 3y ago
  They did, but to get it running as well as they did they had to deviate from generic ARM by adding support for the x86 memory model in hardware. Apple was in a position to do that since they design their own ARM cores anyway, but the off-the-shelf ARM reference designs that most other players are relying on don't have that capability.
  - saagarjha 3y ago
    You can do it with standard ARM instructions these days.
    - _kbh_ 3y ago
      You could always do it with instructions itd just be slow no?.
      - erik 3y ago
        I vouched for this comment, but it looks like you're shadow banned. You might want to email support.
    - mhh__ 3y ago
      > these days Which instructions?
      - saagarjha 3y ago
        Those that are part of FEAT_LRCPC.
  - lonjil 3y ago
    > They did, but to get it running as well as they did they had to deviate from generic ARM by adding support for the x86 memory model in hardware. Note that this is actually very cheap in hardware. All ARM CPUs already support memory accesses that behave similarly to x86. It's just that they're special instructions meant for atomics. Most load and store instructions in Aarch64 don't have such variants, because it'd use a lot of instruction encoding space. The TSO bit in Apple's CPUs is really more of an encoding trick, to allow having a large number of "atomic" memory instructions without needing to actually add lots of new instructions.
mschuster91 3y ago
> It will be interesting to see how that shakes out, going to ARM would complicate backwards compatibility so they would need a very good reason to move. Sticking with AMD for GPUs makes sense no matter the CPU architecture. AMD is competitive on x86, and at the moment Samsung is working out the kinks to integrate Radeon GPUs with their ARM CPUs... so once Samsung has proven the concept works (and, of course, paid for the effort), maybe large consoles will make the switch. It shouldn't be much of a problem for game studios in the end, most games run on one of the household-name engines anyway and they have supported ARM for many years for mobile games.

hypercube33 3y ago

AMD holds an arm license and uses them as part of the software tpu in the pro series processors as I understand. It's not unreasonable to assume they could make some ARM x86 hybrid CPU (like apple did for Rosetta) or a mixed arch chip we've never seen before that can run emulators native. Who knows.

AnthonyMouse 3y ago
But what would be the point of that? If you're already buying it from AMD and the previous generation was x86 so that's what gives backwards compatibility, just do another x86 one. The reason to switch to ARM is to get it from someone other than Intel or AMD.
- lmm 3y ago
  The reason to switch to ARM is to get better performance, especially per-watt. If the supplier that's making your graphics card can deliver that, then why risk onboarding someone new?
  - jwells89 3y ago
    In addition to better perf per watt, it’d allow them to shrink the console, potentially to something as small as a Mac Mini or NUC. Less need for cooling means a smaller console. This could help them make inroads to people who might not have considered a home console before due to their relatively large size. Wouldn’t be surprised if the Switch did well with this market and now MS wants a slice of that pie.
  - isthatafact 3y ago
    > The reason to switch to ARM is to get better performance, especially per-watt. I am not expert, but I cannot remember ever hearing that before. Why would arm have better absolute performance than x86? As a spectator, reading tech press about architectures gave me the impression that even in performance per watt, the advantage arm has over x86 is fairly small, just that arm chip makers have always focused on optimizing for low power performance for phones.
    - lmm 3y ago
      > I am not expert, but I cannot remember ever hearing that before. Why would arm have better absolute performance than x86? Better general design, or easier to include more cache. All the normal reasons one architecture might perform better than another. I mean, you heard about Apple switching all their processors to ARM, right? > As a spectator, reading tech press about architectures gave me the impression that even in performance per watt, the advantage arm has over x86 is fairly small, just that arm chip makers have always focused on optimizing for low power performance for phones. Intel would certainly like you to believe that. But for all their talk of good low-power x86s being possible, no-one's ever actually managed to make one.
      - scheeseman486 3y ago
        There's an anecdote from Jim Keller that Zen is so modular that it'd be possible to swap out the x86 instruction decode block with an ARM one with relatively little effort. He's also been saying for a while now that ISA has little bearing on performance and efficiency anymore. Apple's decision to switch to ARM had many reasons, licensing being just as important as performance, perhaps more so. The low power variants of Zen are very efficient. You're still looking at Intel, but they've been leapfrogged by AMD on most fronts over the past half decade (still not market share, but Intel still has their fabrication advantage).
        lmm 3y ago
        I'll believe that when I see a Zen-based phone with a non-awful battery life. Yes AMD are ahead of Intel in some areas, but they've got the same vested interest in talking up how power-efficient their x86 cores can be that may not actually be based in reality.
mratsim 3y ago
The stuff on the PRO is a Xilinx FPGA, or they have both an ARM Processor and an FPGA?
- deleted 3y ago
  [deleted]
- p_l 3y ago
  The NPUs are effectively hard IP blocks on xilinx FPGA fabric (i.e. there are close to no LUTs there - the chip takes in Xilinx bitstream but the only available resources are hard IP blocks) There's also Xtensa cores (audio coprocessor) and ARM cores included (PSP, Pluton, and I think there's extra ARM coprocessor for handling some sensor stuff optionally)
bradfa 3y ago
AMD has previously made a variety of ARM CPUs, such as the recent Opteron “Seattle” parts. https://en.wikichip.org/wiki/amd/cores/seattle https://en.wikichip.org/wiki/amd/cores/seattle
_kbh_ 3y ago
> AMD holds an arm license and uses them as part of the software tpu in the pro series processors as I understand. AMD uses ARM for its PSP as well which is more than just a TPM. But afaik it also matters what type of license AMD has. AMD would be need an ARM architecture license (like Apple has). This license allows you to do whatever you want with the chip (such as adding a x86 style memory model). The downside to the architecture license is you have clean room design the chip entirely.
mkopec 3y ago
All Zen 1 CPUs and newer have the PSP / ASP security processor which is ARM based and runs before the x86 cores are released from reset. This applies to all Zen models, not just the PRO versions. The fTPM does indeed run on the PSP, so on the ARM cores, among many other things like DRAM training.

dataangel 3y ago

Apple recently demonstrated ARM is pretty capable of emulating x86

jsheard 3y ago
They did, but to get it running as well as they did they had to deviate from generic ARM by adding support for the x86 memory model in hardware. Apple was in a position to do that since they design their own ARM cores anyway, but the off-the-shelf ARM reference designs that most other players are relying on don't have that capability.
- saagarjha 3y ago
  You can do it with standard ARM instructions these days.
  - _kbh_ 3y ago
    You could always do it with instructions itd just be slow no?.
    - erik 3y ago
      I vouched for this comment, but it looks like you're shadow banned. You might want to email support.
  - mhh__ 3y ago
    > these days Which instructions?
    - saagarjha 3y ago
      Those that are part of FEAT_LRCPC.
- lonjil 3y ago
  > They did, but to get it running as well as they did they had to deviate from generic ARM by adding support for the x86 memory model in hardware. Note that this is actually very cheap in hardware. All ARM CPUs already support memory accesses that behave similarly to x86. It's just that they're special instructions meant for atomics. Most load and store instructions in Aarch64 don't have such variants, because it'd use a lot of instruction encoding space. The TSO bit in Apple's CPUs is really more of an encoding trick, to allow having a large number of "atomic" memory instructions without needing to actually add lots of new instructions.

mschuster91 3y ago

> It will be interesting to see how that shakes out, going to ARM would complicate backwards compatibility so they would need a very good reason to move. Sticking with AMD for GPUs makes sense no matter the CPU architecture. AMD is competitive on x86, and at the moment Samsung is working out the kinks to integrate Radeon GPUs with their ARM CPUs... so once Samsung has proven the concept works (and, of course, paid for the effort), maybe large consoles will make the switch. It shouldn't be much of a problem for game studios in the end, most games run on one of the household-name engines anyway and they have supported ARM for many years for mobile games.