Microsoft adds SSE4.2 to the list of compatibility blocks in Windows 11

Although Windows 11 is now approaching its third birthday, hardware requirements remain unchanged. You still need an 8th Gen Intel or 2nd Gen AMD Ryzen processor (or newer) with a few extras to run the operating system in officially supported mode. That requirement is quite easy to bypass, which helped users with old hardware run Windows 11 relatively fine. However, with Windows 11 version 24H2, things are changing.

By now, you probably know that Windows 11 version 24H2 (its preview builds) requires the POPCNT instruction to boot. CPUs without POPCNT can no longer run 24H2 builds, even with existing modifications. Microsoft recently added a corresponding registry to the Windows registry, refuting some speculation that the POPCNT instruction requirement is a temporary measure or a mistake. The setup experience is now also warning about the missing instructions when installing version 24H2 on old computers.

In 26063, the latest Canary build, the list of compatibility blocks received another value (spotted by Deskmodder). "BlockedBYSSE4.2" is now responsible for checking whether your processor supports the SSE4.2 instruction set. You can check it by launching Registry Editor and heading to Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\CompatMarkers\GE24H2.

It may be easy to be upset about Microsoft blocking old hardware from running its operating system. However, keep in mind that SSE4.2 is an instruction set that was introduced sixteen years ago. Whether you like it or not, new features require more modern hardware, so it is natural to see old processors no longer being able to run the OS they were never designed to in the first place.

The entire POPCNT story is anything but new in Microsoft's world. Even Windows 10, which is considered a universally "omnivore" in terms of hardware compatibility, had to drop some chips at one point. Starting with the April 2018 Update, Windows 10 cannot run on specific Intel mobile chips due to bugs in the now-unsupported graphics driver.

If you are still determined to run Windows 11 24H2 on unsupported hardware, check out this guide to learn how to make sure your CPU has the necessary instructions.

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