I'm upgrading my graphics into a Radeon 5770 PCI.E 2.1 GDDR5. After ordering one, I realized a minor problem. My motherboard is fairly old and only has a PCI.E 2.0 x16 slot. Would the 5770 still be able to run on that slot?
Yes, PCI-E 2.0's are fully backwards and forwards compatible between versions, you can use PCI-E 2.1 card in any PCI-E 2.x x16 slot, it doesn't matter if the card is 2.1 or 2.0. However there is some issues found by putting PCI-E 2.1 on 1.x slots with older BIOS, because most probably you need a newer BIOS. You'd better not try if you have older computer and your BIOS can't be updated (BIOS drivers are motherboard drivers). For your information to make my answer stronger, in fact there is no motherboard that is written there 'PCI-E x16 2.1 Slot'.