PCIe 2.1 card in 2.0 motherboard

[Lateralus180]

I purchased two ATI Radeon HD 5870's by XFX that supports PCIe 2.1 and my motherboard only supports 2.0... I put my system together and everything works fine but I get no video signal. I tried both cards in three different slots and nothing. I removed them, and installed my older Nvidia 7800 GTX card which uses PCIe 1.0 and all worked fine. I could see the Asus intro and bios without a hiccup.

My question is, can a motherboard that is designed for PCIe 2.0 support a GPU that is designed for PCIe 2.1? Or are both of my $412 GPU's dead?

If the motherboard can not support the video cards, will I be able to return them to Newegg, and order standard 5870's? Any penalty/restocking fees?

I was told by a friend that the mobo should be able to support the video cards, but the extra speed won't be utized.. that's why I bought them in the first place.

Thanks.

[Evilsizer]

all the reading on pcie 2.1, it does not have any bandwidth increase over 2.0. it simply adds debugging features from what i have gathered. there is also the possibility that the bios needs to be updated. there might be a flag that needs to be add into the bios for the new cards to work correctly. if you bought the cards BNIB from newegg there should be no way they are dead. unless you man handled them for hours before putting them. there is the small change of static-electricity build up but that would be nothing to worry about if you live in a humid climate.

[wingman99]

I just visited another post just like this and it turned out to be his power supply cables, he had both on the same voltage rail. also what's your PSU wattage.