The Windows 11 24H2 update, which Microsoft began testing earlier this month, is set to change the approach to installation requirements. But this really only applies to very old PCs and retro hardware enthusiasts.
According to a post by user Bob Pony on X, the latest builds of Windows 11 refuse to boot on older processors that don’t support an as yet obscure instruction called POPCNT. According to programmer Vaibhav Sagar, this instruction is short for population count, and is used to “count the number of bits in a machine word,” ArsTechnica reports.
So HUGE discovery found in Windows 11 Version 24H2, since build 25905.
A CPU with the instruction “POPCNT” IS NOW REQUIRED!
There are various system files requiring the POPCNT CPU instruction, from the Windows 11 kernel to the USB XHCI drivers.Without POPCNT, it doesn’t boot! pic.twitter.com/vCWYvzfu6k
— Bob Pony (@TheBobPony) February 11, 2024
It’s unclear why POPCNT has become the core instruction for a range of Windows components, but it appears that the Windows kernel, system USB and network drivers, and other core system files now require this instruction starting with Windows 11 24H2.
Modern x86 processors implement POPCNT as part of the SSE4 instruction set. For Intel chips, it was added as part of SSE4.2 in the original first generation Core architecture, codenamed Nehalem. In AMD processors, it is part of SSE4a, first used in Phenom, Athlon and Sempron processors based on the K10 architecture. These architectures date back to 2008 and 2007 respectively.
This effectively prevents mid-2000s Intel Core 2 Duo systems and early Athlon 64-based PCs from booting Windows 11 at all. The change will mainly affect retro computer enthusiasts who make YouTube videos in the genre of “we installed Windows 11 on a potato, let’s let’s see how it works,” rather than users of real systems.
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