PCI-E 3.0 is full compatible with all PCI-E since 2.0 chipset.
Recently i bought "ASUS GTX750 TI OC 2GB DD5", and is running in full power in my following computer;
ACER ASPIRE M7720
CI7 2.66
12 GB RAM DDR3 1333MHZ
PCI-E 2.0 X16
WINDOWS 7 SP1 X64.
I'm playing THIF (2014) with all settings enabled, with a maximum framerate 50. I'm not feeling any performance loss because of my
PCI-E 2.0.
I´ve tested with COD Ghost, Battlefield 4, Crysis 3. All this games are running like "hell", at full power and no performance loss.
So to all people that have any doubts about PCI-E 3.0, i confirm that all GPUs PCI-E 3.0, runs on PCI-E 2.0 at full power.
Thank you Tom´s Hardware, for this post. Because of you I decided to buy my new Graphic card ASUS GTX750 TI OC 2GB DDR5.