Has anyone installed a PCI-e 3.0 card on a PCI-e 1.x mobo?

[iruleeveryone28]

I've had plenty of people tell me it won't be a problem, sadly all of them installed 3.0 on 2.0, so I can't take their word for it.

I've read 3.0 is backwards compatible but details are few and far between about exactly how FAR BACK this backwards compatibility goes.

I emailed Sapphire to inquire about their 7970 working on a PCI-e 1.x board, they said it wouldn't.

Currently waiting a response from XFX, Asus and Gigabyte about their cards.  No reply yet.