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8.1 does not install on existing 8.0 installations

    Question

  • Installed Windows 8 Pro on 4 Windows 7 computers. No issues. Tried to upgrade all 4 PCs to 8.1 and 3 failed to install with error of " ... process doesn't support (some instruction)." Some instructions are: LAHF/SAHF, PrefetchW and ChangeExpress128.  Will shipping 8.1 be different? Is 8.1 just using special instructions for testing. If not, a lot of computers can't be upgraded from 8 to 8.1.
    Tuesday, July 30, 2013 8:16 PM

Answers

  • You missed the point. Win8.1 requires CMPXCHG16B, I asked this the MSFT developer
    Gov Maharaj
    . He told me that he asked the correct team to update the hardware requirement page to show this new/changed requirement.

    Win 8.1 uses CMPXCHG16B to have some optimizations over Windows 8.0.

    MSFT now also shows this requirement inside the FAQ:

    Additional requirements to use certain features:

        For 64-bit installations of Windows 8.1 Preview, your CPU must also support CMPXCHG16b, PrefetchW and LAHF/SAHF.

    http://windows.microsoft.com/en-us/windows-8/preview-faq


    "A programmer is just a tool which converts caffeine into code"




    Tuesday, August 06, 2013 5:39 AM

All replies

  • Were these AMD based machines? Please post the msinfo32 from the machines that failed.

    Tuesday, July 30, 2013 9:12 PM
  • 8.1 requires the CMPXCHG16B cpu feature:

    http://4sysops.com/forums/topic/windows-server-2012-r2-on-virtual-box-error-0x000000c4/


    "A programmer is just a tool which converts caffeine into code"

    Wednesday, July 31, 2013 5:23 AM
  • Well I'm not using virtual box, just installing to wiped clean hardware.  One PC is AMD based, next is Pentium D - 3.0 GHz, next is Pentium 4 - 3.06 GHz, and the last one is not available right now. 
    Wednesday, July 31, 2013 5:24 PM
  • Oh and don't forget, these PCs run Windows 8 just fine.  So why would 8.1 be so different if it's only a point update?

    Wednesday, July 31, 2013 5:31 PM
  • In Windows 8 run AIDA64, go to CPUID and look if the instruction is supported:


    "A programmer is just a tool which converts caffeine into code"

    Wednesday, July 31, 2013 6:46 PM
  • I think we're missing the point.  I don't care what instructions are supported or not, the issue is why is there a difference between 8.0 and 8.1?  I can understand a CPU requirement difference between XP and Vista or between Vista and Win 7.  But why is there a difference between 8 and 8 "blue?"
    Friday, August 02, 2013 8:30 PM
  • You missed the point. Win8.1 requires CMPXCHG16B, I asked this the MSFT developer
    Gov Maharaj
    . He told me that he asked the correct team to update the hardware requirement page to show this new/changed requirement.

    Win 8.1 uses CMPXCHG16B to have some optimizations over Windows 8.0.

    MSFT now also shows this requirement inside the FAQ:

    Additional requirements to use certain features:

        For 64-bit installations of Windows 8.1 Preview, your CPU must also support CMPXCHG16b, PrefetchW and LAHF/SAHF.

    http://windows.microsoft.com/en-us/windows-8/preview-faq


    "A programmer is just a tool which converts caffeine into code"




    Tuesday, August 06, 2013 5:39 AM