A month ago it became known that Intel is forcing motherboard manufacturers to disable support for AVX-512. All manufacturers of Z690 boards based on Alder Lake processors have received a microcode update that completely disables the use of this vector instruction set. At the same time, AVX-512 physically remained on the P cores. It can be activated through the BIOS and increase performance by 14-32 times in some specific tasks, while disabling the little-used E cores. With a microcode update, Intel closed this loophole.
However, not for everyone. MSI disobeyed the "big brother" and included support for the old microcode in at least one of the firmware versions. All owners of the MEG Z690 Unify-X motherboard can be convinced of this.
As seen in the screenshot above, the MEG Z690 offers a choice of two microcode options. Apparently, Normal is the latest version of the microcode, and AVX-512 Trial is the previous version, without the January updates from Intel.
This is quite unexpected and welcome news for users who require this functionality.
In January 2022, Intel removed official support for AVX-512 from the new 12th generation Alder Lake processors. It was originally assumed that this module was physically removed from the chip, because it takes up a lot of space. But then it turned out that the blocks remained in place, but only in the productive P cores.
AVX-512 vector instruction blocks on a Core i9-12900K processor
Shortly thereafter, the community found a way to embed an older version of Intel's microcode into the new firmware, effectively turning the AVX-512 back on. Unfortunately, the choice of the old microcode version forces us to abandon some of the optimizations that Intel has made in recent versions, including performance optimizations for the DDR5 memory controller.
AVX-512 support is found in various applications that benefit greatly from hardware accelerated vector instructions. This is software for mathematical calculations, emulators of various game consoles such as RPCS3 (PlayStation 3 emulator), Yuzu Emulator (Nintendo Switch emulator) and much more.
For sports overclockers, AVX-512 support is also very important to get maximum results in some benchmarks, such as Y-cruncher (multi-threaded calculation of the number of pi with support for vector instructions). This is reported by enthusiast Xavier Amberger on Twitter, who hopes to achieve record performance on an 8-core processor with AVX-512. It was he who first noticed the microcode selection option in the MEG Z690 Unify-X. This option happened after updating BIOS A22 to the latest beta version:
The comments said that after the firmware update, the MSI Z690-A Pro DDR4 motherboard also had an option to rollback to microcode with AVX-512 support.
Intel has not officially disclosed the reason why it banned the use of the AVX-512. Perhaps the reason is the forced shutdown of the E cores when the AVX-512 block is activated, although in some tasks such a replacement (AVX-512 instead of the E cores) has practically no effect on performance or even improves it.
Intel Core i9-12900K testing, source
There is also a conspiracy theory that software disabling AVX-512 in desktop processors creates additional demand for processors for workstations and servers, where the instruction set will continue to work as expected. Detractors suspect that the first seven generations of Core desktop processors deliberately avoided models with more than four cores so as not to hurt the more profitable server segment.
bbabo.Net