AVX 512 on W7

Discussion in 'Operating Systems' started by David Lake, Jan 17, 2020.

  1. David Lake

    David Lake Master Guru

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    I still use windows 7, that is NOT up for debate and software is increasingly trying to use AVX 512 because I have a 9920X and therefore crashes with an unhandled illegal instruction exception.
    I need to either hide the AVX 512 compatibility CPUID returns or somewhat more unlikely, make windows 7 use AVX 512.

    I would pay big money to fix this issue.
     
  2. Astyanax

    Astyanax Ancient Guru

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    Leave feedback that the software should be made properly and check against the feature set list as exposed to the OS instead of assuming support based on cpuid.
     
    Last edited: Jan 17, 2020
  3. RealNC

    RealNC Ancient Guru

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    Check your BIOS. If you're very lucky, it might have an option to either disable AVX 512, or let you specify CPUID levels.
     
  4. Astyanax

    Astyanax Ancient Guru

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  5. David Lake

    David Lake Master Guru

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    I have an Asus X299 SAGE/10G, I dont think there is anything in the bios that would help unless I missed something.
    The first thing that raised this issue is steam VR home because at some point it just stopped working and I couldn't get into the "home" environment and after some digging I found steamtours.exe was crashing right after execution with an illegal instruction exception in phonon.dll which is the audio core, a disassembly shows it tries to execute the instruction vmovss which is an AVX-512F instruction.

    I have opened a help request with steam but their best reply is:
    Hello there,

    Due to settings within Windows 7 and 8 this could be a recurring issue which we will be unable to investigate due to the end of official support for both of the aforementioned Operating Systems.

    I recommend reaching out to the Steam community through the Discussions to see if there are any other users who have experienced this and can help provide you with a possible workaround that they have found.

    Thank you for using Steam,
    Kaz

    Also I have tried the software development emulator but my test application was extremely slow and I doubt it would be of use because the steamtours.exe process that crashes is executed in the background, with the emulator you have to execute the subject process explicitly.

    While I can still play games the next problem was with "The Lab" which runs but has a sound issue and shows an error message on the desktop.

    I can only expect more of these issues as developers implement AVX512 with no regard for older OS's.
     
  6. mbk1969

    mbk1969 Ancient Guru

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    If software crashes due to attempt to use missing instructions it definitely does not check for CPU ID. You can`t fool such software.
     
  7. Astyanax

    Astyanax Ancient Guru

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    The instructions aren't missing, the cpu has them, thats where cpu-id checking is actually a failure - Windows 7 can't use EVEX registers so the most that can be used is up to AVX2

    Windows 8.1 is not end of support.
     
  8. David Lake

    David Lake Master Guru

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    Maybe something similar to the BIOS emulation that was used to crack windows with offline OEM activation could be used, of course this wouldn't be an illegal use of such a thing or maybe some sort of hypervisor.
    We just need someone who knows how to code such software, I code but nothing on that level.
     
  9. David Lake

    David Lake Master Guru

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    The SDE does work but its PAINFULLY slow.
     

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