hey - so I have a bit of an issue. One of my rigs (2x6950, 2x5770) was working fine for months until this morning. I had it offline last night for some maintenance, switching a hard drive - maintenance goes well, no issues and POST is fine after OS install. So I shut it down and go to sleep. Wake up to finish some OS configs and it refuses to POST. None of the usual motherboard beeping, nothing. I didn't move the cards around at all over night - and I've checked cables and slot pressure. The fans spin up but nothing else happens. I've tried taking the 6950s out and running only 5770 and that works, POST is ok. But any number of combinations of 6950 and pcie slots refuses to boot. Even single 6950 cards (tried both) gives no post.
What can I do to troubleshoot this? They're on a Sapphire P67 motherboard which has a diagnostic LED and it prints a code "AB", which might mean "setup input wait", but I have no idea what that means.