this post was submitted on 20 May 2024
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Microsoft says “Prism” translation layer does for Arm PCs what Rosetta did for Macs (arstechnica.com)
submitted 6 months ago by [email protected] to c/technology
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[–] [email protected] 1 points 6 months ago (1 children)

Yes unified and extremely slow compared to an ARM architecture’s unified memory, as the GPU sort of acts as if it was discrete.

[–] pycorax 1 points 6 months ago (1 children)

Do you have any sources for this? Can't seem to find anything specific describing the behaviour. It's quite surprising to me since the Xbox and PS5 uses unified memory on x86-64 and would be strange if it is extremely slow for such a use case.

[–] [email protected] 1 points 6 months ago (1 children)

It’s been a while since I’ve coded on the Xbox, but at least in the 360, the memory wasn’t really unified as such. You had 10 MB of EDRAM that formed your render target and then there was specialised functions to copy the EDRAM output to DRAM. So it was still separated and while you could create buffers in main memory that you access in the shaders, at some penalty.

It’s not that unified memory can’t be created, but it’s not the architecture of a PC, where peripheral cards communicate over the PCI bus, with great penalties to touch RAM.

[–] pycorax 1 points 6 months ago

Well for the current generation consoles they're both x86-64 CPUs with only a single set of GDDR6 memory shared across the CPU and GPU so I'm not sure if you have such a penalty anymore

It’s not that unified memory can’t be created, but it’s not the architecture of a PC, where peripheral cards communicate over the PCI bus, with great penalties to touch RAM.

Are there any tests showing the difference in memory access of x86-64 CPUs with iGPUs compared to ARM chips?