B660 and AVX512

[chameleoneel]

Asus, MSI, and I think Asrock, have been offering an option for AVX-512, on their Z690 motherboards.

I'm wondering if anyone here knows for certain (first hand experience) if they are offering the same option on their B660 motherboards?

 

[bigdogchris]

Not one listed, but I have a Gigabyte B660 and CPUID is reporting AVX512f is active. Prime95 is doing AVX512 workloads.

 

[bigdogchris]

Just updated to F7 bios on my 660 Aorus Master DDR4 and AVX512 has been removed. Change notes do not say it's being removed.

 

[chameleoneel]

I just setup an Asrock Z690 Phantom Gaming-ITX/TB4 on Sunday. I updated the bios to the January 25th bios, which did not have AVX512 support.

Today I noticed that they posted a new bios on Monday. I installed it. It has AVX512.

 

[chameleoneel]

I just setup an Asrock Z690 Phantom Gaming-ITX/TB4 on Sunday. I updated the bios to the January 25th bios, which did not have AVX512 support.

Today I noticed that they posted a new bios on Monday. I installed it. It has AVX512.

And my computer freezes not long after booting into windows. Seems they must have had to come up with a new way to activate it, and its unstable. If I disable AVX512, everything works as it should.

 

[Absalom]

It's a feature that was never meant for production.

A bit of history:

Intel had two separate teams working on Alder Lake's design. One team designed the P-Cores, the other designed the E-Cores. For whatever reason, the E-Core team did not get around to supporting AVX512 instructions (probably due to power budget constraints). So as it stands today, only the P-Cores physically support AVX512 in 12th gen Intel cpus. And that's pretty much that.

Not supporting AVX512 at all must have been a last minute decision on Intel's part. You can't just offload AVX512 workloads from P-Cores to E-Cores as they physically don't support the instructions. In theory, it might be possible to schedule a P-Core to never offload to an E-Core, but I get the impression doing so would be very complex and require the OS in some part to concert it. The whole point of this new architecture is that the underlying hybrid hardware is abstracted from the software. Anyway, Intel didn't want to delay 12th gen launch to hack up some support for AVX512, so they launched the product as-is and pulled AVX512 support as a last minute decision.

The snafu is that Intel didn't actually physically remove AVX512 from the P-Cores. Motherboard makers took note of this, so they unofficially put support in it for some of their products at launch. If you enable it in a Z690 motherboard that supports it, it will simply disable the E-Cores. It doesn't magically make AVX512 work, it just brute forces it by disabling one feature for another. You literally lose your E-Cores for AVX512. Not exactly an elegant solution.

So the fact it's unstable is expected. It's an unsupported feature, one that Intel never intended to make it into production. I doubt it will ever be "officially" supported by 12th gen products.

Raptor Lake might support it. If it does, then the option to support AVX512 is back on the table given that Z690 is supposed to support 13th gen Intel. But we'll have to wait and see how that plays out.

 

[geok1ng]

logged in after a few years just to help :
Maxsun/Soyo chinese maker has a low end brand named Terminator/Classic. Their last BIOS has avx512 available on H610, B660 and Z690 motherboards.

https://www.reddit.com/r/hardware/comments/t7xi5k/soyomaxsun_motherboards_lga1700_chinese/
http://www.soyocn.net/2022/0109/2849.html
You can find these on Aliexpress.
Here is a friend of mine on youtube showing AVX512 on the Z690 model, but it works for B660 models as well, with both C0 and H0 CPUs.

Just remember that only CPUs built last year still have avx512.