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Microsoft wants users to understand why old CPUs cant run Windows 11
Microsoft wants users to understand why old CPUs cant run Windows 11
Microsoft released a major Insider build — Build 26052 — earlier this week to both the Dev and Canary channels. This is also the first Windows 11 24H2 build, and it looks like Microsoft is making some pretty interesting changes to how it supports CPU instruction set architecture (ISA) in the next-generation version of Windows 11. The most notable change is that the SSE4 "POPCNT" specification is now required to run Windows 11. When a user tries to boot into Windows 11 24H2 on a system powered by a processor that doesn't support POPCNT, the PC won't boot.
It appears, therefore, that users running older processors will no longer be able to bypass the Windows 11 24H2 system requirements. This further confirms the need for the POPCNT CPU instruction. When users attempt to install Windows 11 build 26058, the Setup file will throw a message that reads “This PC's processor doesn't support a critical feature (PopCnt),” as seen in the screenshot below.
This is similar to when the previous Windows setup process had a check to see if the NX (Never eXecute) bit, PAE (Physical Address Extension) was enabled, or if SSE2 instructions were present, then the upgrade would be blocked. As a result, PCs running older processors like the Intel Core 2 Quad, like the one in the screenshot above, which are perfectly capable of running basic Windows 11, will not be supported. Microsoft seems to be making the "POPCNT" instruction a requirement in Windows 11 24H2. Obviously, CPUs without it will not boot into Windows.
The POPCNT instruction, which stands for “population count,” counts the number of 1s in binary representation. AMD introduced it in 2006-2007 with the Barcelona architecture, the first true quad-core in the x86 industry. Intel added it later with Nehalem (the first-generation Core i SKU). It’s unclear why Microsoft is mandating POPCNT support for CPUs, but it’s likely that certain features in upcoming versions of Windows will require it.