Microsoft blocks some PCs from Windows 11 24H2 — CPU must support SSE4.2 or the OS will not boot

Windows 11 24H2 has received yet another hardware requirement for users with modded Windows 11 installs to watch out for. Bob Pony on X (Twitter) discovered that the SSE 4.2 instruction set is now required to run Windows 11 24H2, starting with build 26080. If the instruction is lacking, the OS won't boot.

If this sounds familiar to you, this new requirement is very similar to the POPCNT instruction requirement that we reported on several months ago. The only difference is that this new instruction set requires the actual SSE 4.2 instruction set. Previously only the POPCNT instruction inside of the SSE 4.2 instruction set was actually required.

This minute change won't make any difference to Windows 11 users today. All modern systems that support Windows 11 already have SSE 4.2. In fact, SSE4.2 has been around for nearly 20 years, and almost every processor has supported it for just as long. The only users potentially affected are tinkerers and enthusiasts who are trying to mod Windows 11 to run on incompatible hardware.

For one reason or another, Microsoft has decided to increase Windows 11's system requirements starting with version 24H2 which will debut later this year. These new requirements go beyond the original Windows 11 system requirements, consisting of Secure Boot, TPM support, and a Kaby Lake or newer CPU. POPCNT and the SSE 4.2 requirements are new and have been added specifically to 24H2 and will be applied to future iterations of Windows 11 going forward.

Bob Pony re-affirms that SSE4.2 specifically is required, this means that any older CPUs such as AMD's Barcelona chips that only go up to SSE4a won't work (through Windows 11 modding). Bob Pony has even made a Windows 11 24H2 tester that will verify if the latest Windows 11 24H2 builds with the new SSE 4.2 requirement works on your system. But again, this will only apply to an extremely niche subset of Windows 11 users who are customizing Windows 11 to run on incompatible hardware. Systems that can run Windows 11 today or come with Windows 11 will be able to run 24H2 without any problems.