Microsoft's upcoming change could block off Windows 11 CPU requirements bypass on old PCs

Earlier today, we reported about an unofficial WinPE that allows a user to check if their unsupported hardware can run Windows 11 24H2. For example, the creator of the tool confirmed their Intel 3rd Gen processor was capable of running the upcoming Windows version.

The system requirements, and especially CPU requirements, have been a hot topic of debate ever since they were first announced by Microsoft when Windows 11 was publicly revealed. That's because the operating system rendered a lot of still-relevant processors incompatible and unsupported (Intel 7th gen and Ryzen 1st gen CPUs/APUs). The tech giant, though, later did add a few Intel 7th gen chips to the list, but that hardly pleased anyone.

Despite no official support, users have found ways to bypass the requirements and run Windows 11 on fairly old systems with relatively satisfying results. For example, a user with an unsupported Core i5-580M, based on the first-gen "Nehalem" architecture, felt like their system ran Windows 11 22H2 "like magic."

And it does not help Microsoft's decision when its own PC Health check app incorrectly reports that a Pentium 4 is perfectly capable of running Windows 11. Funnily, even a senior Microsoft employee was found running an unsupported processor when live-streaming a Windows Insider webcast.

However, Microsoft is seemingly bringing changes to CPU instruction set architecture (ISA) support that could define how successful the attempts to run Windows 11 24H2 on very old systems will be. Although the unofficial WinPE tool suggests it will work on fairly old CPUs, processors that are even older could fail to do so following this change.

Tech enthusiast and Twitter (now X) user Bob Pony noticed that Microsoft is seemingly looking to make the "POPCNT" instruction a requirement on Windows 11 24H2. Apparently, CPUs that do not have it will fail to boot into Windows.

The POPCNT instruction, short for population count, helps count the number of 1s in a binary representation. AMD introduced it back in 2006-07 with its Barcelona architecture, which was the first true quad-core in the x86 industry. Intel added it later with Nehalem (the first gen Core i series SKUs). It is unclear why the company is making it mandatory. Perhaps certain features in the upcoming Windows version require it.

The instruction has seemingly been in place since an earlier build 25905, which coincides with another previous report where old AMD Turion II and Intel Core 2 Duo PCs were found unable to run Windows 11 via bypass. The situation is a bit reminiscent of the SSE2 support for Windows 7 updates back in 2018.

Bear in mind though that Insider builds are experimental in nature and hence things could change in the future when 24H2 becomes publicly available.

Update Feb 15: Some additional changes have also been made by Microsoft.

Update Feb 16: The single command bypass trick also does not help.