Microsoft recently updated its list of supported Intel and AMD processors. While the company added a few new Ryzen chips including one which has not been released (at least not yet) by AMD, Microsoft somewhat bizarrely removed many Intel CPUs that were previously on the list of compatible processors.
Aside from updating its list, Microsoft may also be working on blocking Windows 11 installs on unsupported hardware. German website Deskmodder reports that one of its forum members was unable to install Windows 11 on their Intel Core 2 Duo T6500 system. The user is an Insider flighting the Canary channel when Windows 11 build 25905 installation was seemingly blocked on their PC, even though previous builds worked fine. AMD"s Turion II P650 [sic?] also did not work.
Interestingly, replacing the install.wim Windows Image file of previous builds with that of build 25905 apparently led to blockage of installs on those earlier releases, confirming the tech giant has certainly made some change there. Bypass options like those provided by tools like Rufus and Ventoy, among others, may not be enough. Others like the TPM bypass may not work either.
While Microsoft maintains its list of compatible CPUs, people have often run Windows 11 on unsupported chips. And such users have had decent experiences most of the time. assuming they have a somewhat new system. For example, a Reddit user once exclaimed that their Core i5-580M ran Windows 11 version 22H2 "like magic". Funnily, even a senior exec from the company was once seen sporting an unsupported part during a Windows Insider webcast. The SKU in question here was a Kaby Lake mobile Core i7-7660U.
Microsoft has in the past mistakenly offered Windows 11 upgrade to users on unsupported hardware. The PC Health Check app also once gave the Pentium 4 chip a thumbs up for installing the OS.