"Jumping" behaviour of QPC AFAIK is happens only on really old motherboards of Pentium1 era. But in this thread fraggle already posted link stating other (more modern) bug in QPC implementations on different platforms: http://www.virtualdub.org/blog/pivot/entry.php?id=106


By DX9 I mean any application that initializes Direct3D9. And calling timeBeginPeriod has system level influence.