Yes, PCI-e 3.0 GPUs are backwards compatible. I have a HD 7750 (which is a PCIE 3 card) in a old Dell system that only has a PCIE 1.1 slot.
Not fully. There are lots of issues with new 3.0 cards not working on old 1.0 boards. Everyone hoping to revive an old system with a 750ti are having issues. 1.1 also has it's issues with 2.0 cards sometimes.
Yes, PCI-e 3.0 GPUs are backwards compatible. I have a HD 7750 (which is a PCIE 3 card) in a old Dell system that only has a PCIE 1.1 slot.
Not fully. There are lots of issues with new 3.0 cards not working on old 1.0 boards. Everyone hoping to revive an old system with a 750ti are having issues. 1.1 also has it's issues with 2.0 cards sometimes.