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.
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.
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.
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?
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.
> 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.
> 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.
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).
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.
You won't see that happen because AMD have no interest in targeting phones. Why bother? Margins are thin, one of x86's biggest advantages is binary backwards compatibility but that's mostly meaningless on Android, there's additional IP and regulatory pain points like integration of cellular modems.
Intel tried and ran into most of those same problems. Their Atom-based SoCs were pretty competitive with ARM chips of the day, it was the reliance on an external modem, friction with x86 on Android and a brutally competitive landscape that resulted in their failure.
Regardless of architectural advantages from one vendor or another, the point remains that the arguable preeminent expert in CPU architecture believes that ISA makes little difference and given their employment history it's hard to make the argument of bias.
> Intel tried and ran into most of those same problems. Their Atom-based SoCs were pretty competitive with ARM chips of the day, it was the reliance on an external modem, friction with x86 on Android and a brutally competitive landscape that resulted in their failure.
The way I remember it the performance and battery life never quite lived up to what they said it would.
> Regardless of architectural advantages from one vendor or another, the point remains that the arguable preeminent expert in CPU architecture believes that ISA makes little difference and given their employment history it's hard to make the argument of bias.
Current employer is a much heavier influence than prior employers, and someone who's moved around and designed for multiple ISAs and presumably likes doing so has a vested interest in claiming that any ISA can be used for any use case.
There's a long history of people claiming architecture X can be used effectively for purpose Y and then failing to actually deliver that. So I'm sticking to "I'll believe it when I'll see it".
My impression from the tech press/tabloids is that apple was somewhat forced to switch away from Intel because Intel had begun to stagnate. Intel was stuck doing 14nm+ iterations and could only ship slow inefficient chips, resulting in very noisy and hot apple laptops.
Maybe apple could have stayed with x86 from AMD with some sort of co-design, but apple likely preferred to design their own chip so they would control the whole process and keep more of the profits. Designing their own chip also seems like it allowed apple to leverage their investments in TSMC for making their phone chips to also include their laptop chips. I wonder whether they already had a long term plan to dump Intel, or whether the plan started as a reaction to the serious problems that began developing at Intel years 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.
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)
> 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.
> 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.
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.
> 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.
If you wanna play semantics, and argue that the demonstration requires a M-Something chip, then they have in a $599 iPad Air with M1. Or I guess a Mac Mini with M2 for the same price.
If you want to be more lenient, the $129 Apple TV has A15 which is ~same design, but with less cores.
