About PC cannot upgrade to Windows 8.1 with CPU dosen't support CMPXCHG16B

It doesn't affect the 32-bit x86 version of Windows 8.1, only 64-bit x64 version of Windows 8.1 is affected.

Affected hardware that cannot install 64-bit version of Windows 8.1:
CPU: some AMD Athlon 64 X2 and Opteron
Motherboard: some P35 and P45 chipsets

My motherboard is P31 chipset GA-EP31-DS3L (Rev 1.0) BIOS F5F, it's able to install both 32-bit and 64-bit version of Windows 8.1