I just built a new system, and it boots with fans spinning, but my Asus 6870 appears to give no signal to my screen (the screen works with other PCs). So I switched it out with a 5770 from another computer, which was working fine, and this did not solve the problem. However, once I put it back in the other computer, that computer now had no video signal as well. Uh-oh.
The 6870 had 16 pins, and thus I used the cable labeled "PCIE 8-pin" as well as the included two molex-to-8pin adaptor. The 5770 just needed the PCI-E 8pin. In both cases, I have tried multiple monitors, and I am sure the graphics card is well lodged in place. The fan on the GPUs was spinning in every case.
The previosly known good vide card now not working is indeed cause for concern...
It is possible for MBs or PSUs to zap any installed card, but, it is rare....unless it happens.
Double check that you have gpu aux input power (some need a pair) connected...
I'd not advise putting in another GPU to test this theory after the last result! (PS....never pull/reinstall any cards with power applied to rear of PSU due to trickle/wake on LAN/etc. voltages still present in MB...
Just to be sure did you make certain that the 5770 was properly inserted back into the system you took it from? Make sure it's all the way in that PCI-E slot. Also make sure that the PCI-E cable is in all the way. Yes I actually did have a system that didn't boot because I thought the PCI-E cable was fully inserted and it was not.
I checked both DVI outputs on both cards, and I reseated then 2-3 times each to make sure... Regarding the PSU-zapping, isn't it a bit odd that it would fry the GPUs but not the Mobo/RAM? I can hear the hard drive spinning, so it seems to be booting fine apart from the video signal being missing.
The ASUS P7P55D-E LX mobo li up the red "memok" LED on first boot (which had no video signal), so I hit the MemOK button, it rebooted, and the LED never lit up again... if that helps at all.
Any idea how I could verify that my PSU is doing this?
Er. Wow. Thanks for your help guys but I've been both stupid and unlucky:
1. The second GPU which wasn't working no matter what I tried magically started working again. I have no idea what happened.
2. The RAM slots on my mobo are the other way around, so I had to put the RAM starting with the second slot rather than the first slot. Rookie mistake there.
3. The RAM thing didn't help, but when I tried a third, half broken GPU which I was going to throw out anyway, the system suddenly booted. So I put the original GPU back in, and the whole thing now works.
Go figure. Thanks for your help, sorry if I wasted any of your time, heh.