It’s common knowledge that Windows XP won’t run on a 386, or Windows 95 on an original IBM PC. However, with the latest releases of Windows 11, the requirements seem to be shifting. According to an article in The Register, the newest Windows 11 24H2 update may not be compatible with older machines.
The compatibility issue revolves around the POPCNT CPU instruction. Posts on Twitter by TheBobPony reveal that this instruction is present in various Windows 11 system files, such as the kernel and USB XHCI drivers. This means that any CPU incapable of executing this instruction will not be able to boot Windows 11. POPCNT was first integrated into AMD’s Barcelona architecture in 2007 and Intel’s Core processors in 2008. It is an instruction used for counting set bits in a word.
As a result, older CPUs will be unable to run the latest version of Windows 11. It could be due to Microsoft engineers enabling more modern CPU instructions during compilation. However, considering that the affected hardware is over 15 years old, it is likely that Microsoft is willing to exclude these machines from using the latest versions of its primary operating system. This phenomenon has been discussed earlier as well.
If you are running very old hardware, it is advisable to closely monitor Windows updates. Share your thoughts in the comments if this will affect you.
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