On Sun, 23 Jun 2013, H. Peter Anvin wrote:
Why do you care about performance when PAT is disabled?
It will regress already slow boxes. We blacklist a LOT of P4s, PMs, etc and nobody ever took the pain to track down which ones of those actually have PAT+MTRR aliasing bugs.
These boxes have boards like the Radeon X300, which needs either PAT or MTRR to not become unusable...