But Microsoft can do that too? They can compile one version of each DLL for SSE2 and another for AVX or whatever if they want, same as any other vendor. It's no

But Microsoft can do that too? They can compile one version of each DLL for SSE2 and another for AVX or whatever if they want, same as any other vendor. It's not like they can just turn off SSE2 for everybody, because it would break every program, and even new programs may use SSE2 instructions in combination with newer x86 extensions. Even if they did (and I'm not sure it's even possible in x86), I don't see how it could increase security anyways; any new Spectre vulnerability or whatever is probably going to be just as exploitable if not more so using AVX load instructions as SSE load instructions.