Card not working in first PCI-E slot

Hello everybody.

Since sending a motherboard in for rma is both money-sink (need to ship it to them, a replacement unit and to reinstall windows) and an excruciating wait (weeks? months?) I'd like to try absolutely everything I can before I do.

Two months ago everything was working fine, then I had to take everything to another room to paint the walls in my room. Start getting "display drivers stopped working" as I plug the unit back, this over the span of three days. Case was cleaned last month, I decide to take out gpu and clean some more. Turn outlet and psu off, as soon as I start unscrewing the dvi cable I can feel static. Unplug psu, discharge power with the case button, take 6870 out and remove that little dust there was, put it back: gpu is powered up, fan spins, permanent black screen at boot, no video signal. Take it off, hook the thing to onboard gfx: everything works fine. Try back with 6870, black screen. Go get PSU tested, it apparently works (they didn't give me a full report on load). Go back, test mobo with three different older ati (pre-amd) cards, 3x black screen. Checked bios to make sure, main adapter was on pci-e.

I had other stuff to do so I put the issue to rest for a few days while I had one of the ati cards (2600 xt) double-checked by a store. As it turns out, the 2600 xt works alright, so I decided to take the plunge and go with a z77-a motherboard to replace the asrock (very cheap and couldn't even overclock so). After putting the whole thing back together, it turns out that I still have the same issue. As I set the motherboard on PCI-E, it reverts back to auto (and thus onboards) every time, like it doesn't care I tell it to just go PCI-E.

I managed by pure accident (during boot) to rapidly swap cables between onboard and gpu, and the card miraculously worked, for both monitors, it was giving response in catalyst, temperature and everything, but it was short-lived as the next time I rebooted it got me back to square one.

At this time this was the psu I had

http://www.ms-tech.de/eng/index.php/product/detail/pdci...

It was the only thing resembling a tolerable psu in this godforsaken town I could find when my modxstream died.

So, I finally decide to move to a thermaltake berlin after a friend borrows me a gtx285 which shows the exact symptoms as my 6870 (static, no boot).
I put all cables in place, I seat the card and...it works. It was *also* a PSU issue. It leads me to the desktop, where I download the latest catalyst. Setup needs to reboot so I do, and then black screen again. I think it may have been shifting back to onboard, so I force it to PCI-E like I did before. This time it accepts it, and as a result it's permanently stuck to black screen. Reset bios, back to work. Uninstall completely onboard graphics, it's stuck again, reset again.

At this point, fresh windows install. Insert card after very first windows boot, no good. Last resort: try again second pci-e slot, it works, it boots to the desktop, it accepts catalyst and it works just fine, I'm posting this very message from the rig the card is outputting graphics for.

For the heck of it, I try a 2600xt in the main slot and once again, it boots with signal, before getting to the desktop I turn it off, plug a 6870 and it works, it brings me to the main screen. Then, it starts looking for drivers, and from the small log in the corner it tells me it installed it as a 6870, which is what should happen. The last attempt saw the 2600xt booting me to the desktop before getting bsod, and the gtx285 on the second slot working fine.

That's the thing, I haven't installed anything other than 14.9 Catalyst the first time I got the 6870 to work on this mobo. As soon as I did install drivers, card stopped POSTing. Completely removed Catalyst, rebooted, still no POST. When I swap things around I don't get to the desktop and install drivers, all that matters to me is that the thing POSTs while the card is stuck inside. It refused to do it with a 6870, a 285gtx and a 2600xt in slot one, exception made for the latter card which did actually POST but bluescreened me right before getting to the desktop (afaik card could be very well dying as it runs pretty hot and the last time I tried it on the older motherboard it did work but that lasted about thirty minutes, after which it lost video signal and it shut itself down). Slot 2 works flawlessly instead (been running 6870 in slot 2 for over three straight days now, benchmarked it and it provides 2297 on Graphics Mark 3D (avg is ~2500, probably it's because of the x4 speed), so there is either some option I'm missing (I'm not sure but I doubt it) or the slot 1 is going crazy.

While waiting for a reply in here I actually took the effort of breadboarding the rig after removing and reinstalling cpu and heatsink, so it can't be a short issue or whatever. Literally the only thing I haven't tried yet is another format and fresh boot with a different card like the gtx285.