Is PCI express 3.0 backwards compatible with the other revisions? I read on Wikipedia that this was going to be attempted, but I can't find anywhere this is confirmed.
closed as off topic by MDMarra, Ward, Chris S, Zoredache, Shane Madden♦ Nov 28 '11 at 1:43
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Yes. The cards and bus (per card) will operate at the lowest common speed that both support.
Wikipedia: PCI Express mentions
PCIe 3.0 Base Spec §4.2.2 elaborates: