Windows 8.1 64 Bit Not Working With Some Old AMD Processors

/ 4 years ago


Microsoft recently made a statement to Neowin confirming that some really old AMD processors would experience issues running Windows 8.1 64 bit. Microsoft claim that some early AMD processors (such as the Athlon 64, Athlon x2 64, Opteron 185) cannot run Windows 8.1 64 bit due to the fact they are missing the CMPXCHG16b instruction set. Windows 8 64 bit did not pose the same problem as that OS had a special software implementation that meant these older CPUs still worked. Microsoft has since removed that support in Windows 8.1 64 bit. Old AMD CPU owners could still run 32 bit Windows 8.1 without any issues, just not the 64 bit.

“This was a change done to improve the security effectiveness of Windows by removing code that cannot use instructions such as CMPXCHG16b. Based on our data, the number of affected processors are extremely small, since this instruction has been supported for greater than 10 years.”

While its never nice to see support for hardware dropped from an OS, the fact most of these unsupported processors date from 2002-2006 suggests that if you’re still running them it really is time for an upgrade. If you’re a die hard “non-upgrader” then you’ll have to stick to 32 bit for now.

SEE ALSO:  Watch the Full AMD Capsaicin Presentation at Siggraph 2017

Image courtesy of AMD

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12 Responses to “Windows 8.1 64 Bit Not Working With Some Old AMD Processors”
  1. Ujlakycs says:

    I had this issue. Wanted to try the new OS, on the old machine with a first generation A64 X2 3800+
    There were random restarts, even during the installation process. But I have this with the 32 bit edition as well.
    The machine working fine by the way with win 7, no problem

  2. γιαννης says:

    seriously since when microsoft cares? we still wait for that “patch” from microsoft about the bulldozers to be able to run multithreads in windows core….. screw them up no one cares as long as they dont fix their OS i will not even think to upgrade from 7 to 8..

    • Klimax says:

      Those patches are already out for quite some time. Too bad they didn’t help at all because BD is too broken architecture with such set of considerations, which prevents any sane perforamnce extractions. (A thread per module to prevent resource sharing, but as few modules to turboboost, while trying to mix threads in such way to complement instruction streams and yet get threads sharing L2-sized data into one module so L2 can be shared. Not solvable at all.)

  3. Anthony Burt says:

    If you’re a die hard non upgrader you’re probably still on Win Xp = No biggy.

    • Jordi VanWinkle says:

      Thats what I was thinking

    • True to an extent. I know for a lot of home users that’s true but I know a lot of people who’s businesses tend to upgrade operating systems but not upgrade the hardware because actually operating systems have become “easier to run” as we’ve moved from XP to 7/8.

  4. Zeros says:

    Yeey I have Athlon x4 635 :D.. not that I care, Windows 7 Ultimate FTW!!!

  5. Mick Maister says:

    I have a Core i5 3570K and still not convinced to move to Win8.. W7 Rules!…. Waiting for “Windows X”

  6. Franc Gorenc says:

    Just checked with Coreinfo app. Athlon 64 3000+ (2GHz, Socket 754, Venice core) does not support CX16, only CX8. gg wp XD

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