Windows 11 officially requires TPM 2.0, secure-boot enabled, and an AMD Zen+ (Ryzen 2xxx) or later or an Intel Core Gen 8 or later.

https://arstechnica.com/gadgets/2021/10/windows-11-the-ars-t...

> ... the best rationale for the processor requirement is that these chips (mostly) support something called “mode-based execution control,” or MBEC. MBEC provides hardware acceleration for an optional memory integrity feature in Windows (also known as hypervisor-protected code integrity, or HVCI) that can be enabled on any Windows 10 or Windows 11 PC but can come with hefty performance penalties for older processors without MBEC support.

> Another theory: older processors are more likely to be running in old systems that haven’t had their firmware updated to mitigate major hardware-level vulnerabilities that have been discovered in the last few years, like Spectre and Meltdown