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Very interesting to see how they bailed on using an IHS over the two dram modules ON the processor die! I love how you can see "reach" engineering solutions in

Very interesting to see how they bailed on using an IHS over the two dram modules ON the processor die! I love how you can see "reach" engineering solutions in apple products, it's clear that they realized the ram would be too large to fit under an IHS and just decided to go with what ended up in the M1 Mac Mini. Very much hoping apple starts allowing even third party nvidia drivers again for latest gen GPU's...

ralfd 6y ago
What does IHS mean?
- jakemauer 6y ago
  Integrated heat spreader, I believe.
  - mark-wagner 6y ago
    Yes, and if you look at the at the IHS it looks like it was intended to cover the RAM, but couldn't, so they just chopped that part of it off.
- rowanG077 6y ago
  integrated heat spreader
spijdar 6y ago
Unfortunately it looks like they're taking the opposite approach, and phasing out even AMD drivers, with eGPUs apparently (?) not supported on M1 devices. It seems they want to phase out all non Metal APIs. (Which is to say, I bet the return of eGPUs on mac will only happen if apple releases a discrete Metal-based GPU) It makes sense, so far as it means they can further integrate hardware solutions they make themselves and not deal with a higher level driver interfaces. Otherwise they'll be limited to incorporating features present in all supported vendors.
- osy 6y ago
  > and phasing out even AMD drivers, with eGPUs apparently (?) not supported on M1 devices. It seems they want to phase out all non Metal APIs. That doesn’t make sense as Metal APIs are implemented on top of the graphics drivers. There’s Metal drivers for AS, Intel iGPU, and AMD. The last two are not built for arm64. On AMD’s side it would require work from AMD as most of the driver is shared code from Windows. I wouldn’t be surprised if that changes in the future.
  - spijdar 6y ago
    You're right -- I didn't mean to imply that's why eGPUs aren't supported right now, I meant I suspect it's a policy change, and Apple plans to move to more integrated drivers in the future, so in "Courage!" fashion, they've preemptively ditched it. I can't imagine there's a hard technical reason why they couldn't support eGPUs. I've used both AMD and nvidia Linux drivers on a ppc64le workstation -- I'd be surprised if porting to darwin/arm64 was that much work. Their endianness matches -- though the difference in page sizes might be a problem. On Linux, some drivers just assume 4kb page sizes, and updating them is really difficult[1]. But AMD and Intel GPU drivers are fine with non-4kb at least, so... [1] https://bugs.freedesktop.org/show_bug.cgi?id=94757 https://bugs.freedesktop.org/show_bug.cgi?id=94757
- X-Istence 6y ago
  I think part of the issue with the eGPU as mentioned in the forum post that is linked is that the drivers haven't been compiled for arm64. So maybe they will bring it back once the drivers are stable enough?
ebg13 6y ago
> it's clear that they realized the ram would be too large to fit under an IHS This is exactly the same design they used in the A12X and A12Z ( see: https://en.wikipedia.org/wiki/Apple_A12X https://en.wikipedia.org/wiki/Apple_A12X ) They clearly do have room for a larger IHS that covers the RAM too, but either this makes manufacturing cheaper since they didn't have to change anything from the previous rev or there's actually a real benefit to not dumping excess core heat directly into the RAM (seems more likely). Sinking heat is great, but only if the temperature differential points away from what you're trying to cool.
- batt4good 6y ago
  Interesting! Thanks for the info!

ralfd 6y ago

What does IHS mean?

jakemauer 6y ago
Integrated heat spreader, I believe.
- mark-wagner 6y ago
  Yes, and if you look at the at the IHS it looks like it was intended to cover the RAM, but couldn't, so they just chopped that part of it off.
rowanG077 6y ago
integrated heat spreader

spijdar 6y ago

Unfortunately it looks like they're taking the opposite approach, and phasing out even AMD drivers, with eGPUs apparently (?) not supported on M1 devices. It seems they want to phase out all non Metal APIs. (Which is to say, I bet the return of eGPUs on mac will only happen if apple releases a discrete Metal-based GPU) It makes sense, so far as it means they can further integrate hardware solutions they make themselves and not deal with a higher level driver interfaces. Otherwise they'll be limited to incorporating features present in all supported vendors.

osy 6y ago
> and phasing out even AMD drivers, with eGPUs apparently (?) not supported on M1 devices. It seems they want to phase out all non Metal APIs. That doesn’t make sense as Metal APIs are implemented on top of the graphics drivers. There’s Metal drivers for AS, Intel iGPU, and AMD. The last two are not built for arm64. On AMD’s side it would require work from AMD as most of the driver is shared code from Windows. I wouldn’t be surprised if that changes in the future.
- spijdar 6y ago
  You're right -- I didn't mean to imply that's why eGPUs aren't supported right now, I meant I suspect it's a policy change, and Apple plans to move to more integrated drivers in the future, so in "Courage!" fashion, they've preemptively ditched it. I can't imagine there's a hard technical reason why they couldn't support eGPUs. I've used both AMD and nvidia Linux drivers on a ppc64le workstation -- I'd be surprised if porting to darwin/arm64 was that much work. Their endianness matches -- though the difference in page sizes might be a problem. On Linux, some drivers just assume 4kb page sizes, and updating them is really difficult[1]. But AMD and Intel GPU drivers are fine with non-4kb at least, so... [1] https://bugs.freedesktop.org/show_bug.cgi?id=94757 https://bugs.freedesktop.org/show_bug.cgi?id=94757
X-Istence 6y ago
I think part of the issue with the eGPU as mentioned in the forum post that is linked is that the drivers haven't been compiled for arm64. So maybe they will bring it back once the drivers are stable enough?

ebg13 6y ago

> it's clear that they realized the ram would be too large to fit under an IHS This is exactly the same design they used in the A12X and A12Z ( see: https://en.wikipedia.org/wiki/Apple_A12X https://en.wikipedia.org/wiki/Apple_A12X ) They clearly do have room for a larger IHS that covers the RAM too, but either this makes manufacturing cheaper since they didn't have to change anything from the previous rev or there's actually a real benefit to not dumping excess core heat directly into the RAM (seems more likely). Sinking heat is great, but only if the temperature differential points away from what you're trying to cool.

batt4good 6y ago
Interesting! Thanks for the info!