The problem with hybrid x86

Published: 3rd January 2022 | Source: Igor's Lab | Author: Mark Campbell

Intel's removing unofficial AVX-512 support from its Alder Lake series processors

Intel's Alder Lake processors have a problem, and that problem is their fragmented AVX-512 support. Officially, Alder Lake doesn't support AVX-512, but unofficially, Intel's Alder Lake processors can support AVX-512 when only Intel's P-Cores are enabled when using with compatible motherboards.

This has created circumstances where Intel's Alder Lake processors can deliver higher performance levels when Intel's efficiency-focused E-cores are disabled, highlighting an area where Intel's hybrid x86 architecture is limiting the performance of the company's latest processors. This is an embarrassing problem for Intel's hybrid processors, and it looks like Intel has started cracking down on motherboard makers who are offering unofficial AVX-512 support with their motherboards.

According to Igor's Lab , Intel has released new microcode for their Alder Lake series processors that will completely disable AVX-512 support. This means that new BIOS revisions for Intel 600-series motherboards will not support AVX-512 under any circumstances. These BIOS releases come before the launch of Intel's rumoured P-Core only desktop Alder Lake CPU models, which are due to be revealed at CES 2022.

With Alder Lake motherboards being amongst the first to support DDR5 memory and PCIe 5.0 devices, Intel's latest microcode updates could increase the performance and stability of Intel's new 12th generation platform. This places fans of AVX-512 in a terrible position, as older BIOS revisions support it, but newer BIOS revisions could contain useful tweaks.

AVX-512 is a useful feature for many users

While AVX-512 is not a widely used set  of extensions,  it has the potential to significantly increase Alder Lake's performance in select circumstances. In November 2021, the creators of the RPCS3 emulator noted that it could increase the framerate of their PlayStation 3 emulator from 68 FPS to 78 FPS in God of War Ascension, which is a huge performance gain.

AVX-512 support is an area that Intel plans to improve upon with their future Hybrid X86 processors. Intel's 13th Generation Raptor Lake CPUs reportedly support AVX-512 when hybrid x86 is enabled, giving Raptor Lake a significant advantage over Alder Lake in supported workloads.

Intel's reported clamp down on Alder Lake AVX-512 support is disappointing, as it relegates a lot of Alder Lake's P-Core silicon to idle nothingness, wasted die space that should now be seen as an inefficiency in Alder Lake's design.

For Intel, it makes sense for them to fully disable AVX-512 on their Alder Lake series processors, especially now that they have P-Core only models on the horizon. As it stands, AVX-512 is a reason for Alder Lake users to disable E-Cores, and a potential feature that could make their P-Core only models faster than their higher-end hybrid counterparts in some workloads. Fragmented/unofficial AVX-512 support on Alder Lake only serves to make Intel look bad. That said, cracking down on such a useful feature is making Intel appear anti-consumer.

You can join the discussion on Intel's crackdown unofficial Alder Lake AVX-512 support on the OC3D Forums .

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