Windows 11 24H2 won't boot if the PC does not support this CPU feature

Microsoft is changing the system requirements of the upcoming Windows 11 24H2 feature update. When Microsoft released Windows 11, it changed the minimum system requirements significantly. This locked out millions of Windows 10 devices from the upgrade to Windows 11.

Now it appears, that Microsoft is modifying the system requirements of Windows 11 again. This is the first time that Microsoft is changing the system requirements of an already released operating system.

Here is what happened: Back in February 2024, testers of Windows 11 started to notice that the operating system would not install anymore on certain devices. The issue was identified quickly as a new restriction regarding a device's processor.

If the processor did not support so-called POPCNT instructions, Windows 11 test build installations would fail. Upgrades from earlier versions of Windows 11 would fail as well.

In other words: the new system requirements introduced in Windows 11 24H2 would prevent some customers from upgrading their devices to the new version.

It became clear soon thereafter that the main new requirement is  SSE4.2.  The processor needs to support SSE4.2 to upgrade a device to Windows 11 version 24H2 or install the operating system on such a device.

Processors released in the last decade support the instruction. Processors that do not support it are not officially supported by Windows 11. Still, it was possible, until now, to bypass the requirements and install Windows 11 on these devices.

Windows 11 won't boot if the processor does not support SSE 4.2

Twitter user BobPony discovered that Windows 11 build 26080 is now preventing the booting of the operating system, if the processor does not support SSE4.2.

Windows 11 will reboot the device automatically on unsupported devices according to the Twitter user's tests.

He writes: "UPDATE: Since Windows 11 Build 26080, a CPU with the SSE4.2 instruction is ALSO REQUIRED TO BOOT Windows 11 Version 24H2!!

Attempting to boot Build 26080+ on systems without the SSE4.2 instruction present will trigger an automatic reboot once it reaches the boot screen phase."

Microsoft has added SSE4.2 as a blocker to the compatibility list. This means that upgrades to Windows 11 24H2 won't be offered on systems that do not support SSE4.2

Customers are stuck

Customers who upgraded their Windows devices to Windows 11 are stuck on Windows 11 version 23H2, if the system's CPU does not support SSE4.2.

Windows 11 version 23H2 reaches end of support in October 2025. This is also the month that Windows 10 will reach its end of support. One option that affected users have is to downgrade their devices to Windows 10. Microsoft plans to allow customers to extend support by up to three years, for a price. This moves the end of support to October 2028.

Another option would be to make the switch to Linux between now and end of support in October 2025.

What about you? Which operating system do you use at the moment?