If you own a PC with an older AMD processor inside and tried to update from Windows 8 to Windows 8.1 this past week, you might have discovered that Windows no longer supports that chip. Today, Microsoft has confirmed to Neowin that it has eliminated support for a number of older AMD chips in Windows 8.1 that lack certain software instructions.
We were alerted to this a few days ago by Neowin reader "eladbs" who told us:
Short story: AMD's early CPUs, i.e. Athlon x2 64, Opteron 185 lack CMPXCHG16b instructions. Until Windows 8 (apparently) MS implemented a software solution into the OS to support this instruction (so I read). Windows 8.1 refuses to install on machines based on those CPUs. Windows 8 works great.
We contacted Microsoft for comment and received a response from a spokesperson. The statement confirms the removal of Windows 8.1 support for these AMD chips, adding:
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.
Obviously, people who are affected by this issue might wish to consider upgrading their PC with a more recent processor or motherboard so they can utilize Windows 8.1.
Update: It's been pointed out in the comments that the 32-bit version of Windows 8.1 could still work, although it's been shown that most PCs running Windows 8.1 are using the 64-bit version.
Image via AMD