I don't know why it's happening , i saw in few games i got nearly 30-40 fps average. I played Black Flag , it's good enough 50-60 fps at ultra but some old games like GTA 4, Arkham City, crysis in which i'm totally shocked at all settings on ultra i get only 30-40 avg fps sometimes stable at 30..At arkham city with physX on & rest at all maximum i got 40-50 avg , lowest i got 25-30..& in GTA 4 too 40 -50 fps at ultra...My system spec: CPU: i5 3570k , RAM: 4x2 GB DDR3 1333 MHz, GPU: Asus DirectCUII GTX 760 2GB oc, PSU: XFX pro 550w , Case: CM HAF 912 mid tower , MB: GA H61m-D2H. OS: windows 7 64-bit (service pack 1).