http://www.pcgameshardware.de/Battle...ows-8-1091767/
!!
Supposedly it is down to DX11.1 which is supported by Windows 8:
http://www.guru3d.com/news_story/bat...rformance.html
There is also a new patch for the game which is being released which will fix the odd performance with the FX63** CPUs(should be quicker than a Phenom II X6 I suspect).