On: Google developing own CPUs for Chromebook laptops

[ndesaulniers]

You're confusing MSRs (which don't have to be saved/restored on context switch) with GPRs (which do).

[ithkuil → ndesaulniers]

Well if there is a truly undocumented extension, how do I know it doesn't come with it's own registers (e.g. like a floating point unit does)

[saagarjha → ndesaulniers]

Apple reserves certain MSRs that apply on a per-process basis, and thus must be applied on context switch.