Windows 11 to Stop Supporting PCs With Older CPUs Lacking Key Instruction Set
• Windows 11 version 24H2 won't boot on PCs with older CPUs that lack the "POPCNT" instruction, which became common in late 2000s CPUs.
• POPCNT is used for counting bits in a machine word, and is now required by many core Windows 11 components.
• POPCNT was introduced with SSE4.2 on Intel Core CPUs in 2008, and with SSE4a on AMD Phenom CPUs in 2007.
• This effectively bars Windows 11 from booting on mid-2000s Intel Core 2 and early AMD Athlon 64 chips.
• Windows 11's official CPU requirements seem to be driven partly by support for advanced security features like "mode-based execution control."