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ATI 5870 running in x8 PCI Express problem

Last response: in Graphics & Displays
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March 28, 2010 8:50:44 PM

Hello all, I am having a strange problem (if you can call it that) where my 5870 is running in x8 mode. Checked via GPUZ, CPUZ and CCC. I have an Asus P6T SE motherboard and it is 100% in the right slot with no other cards in what so ever. I know it must be a problem with either the card or the mobo but which is the most likely? I have no other parts to test with.

The worst part is those are the only 2 components in my PC that I got 2nd hand so I can't return them. I get 22,000 in 3DMark Vantage with my i7 920 and this card so it looks like performance is ok. My worry is that I want to buy a 5970 so I can go Trifire but would I get a hit in performance with this problem? If it's the mobo then both cards might go x8 but if it's my card then one would be x8 and the 5970 would be x16! Not sure what that would do...if it even worked at all.

Any helpful advice would be most appreciated, I have followed this forum and site for years but only just joined myself. I don't usually get problems I can't solve but this is a weird one. Thanks.
a c 230 U Graphics card
March 28, 2010 9:11:10 PM

The x6 thing starts to have a performance hit with the 58xx series however it's not that big.....with the 5970 it would be an issue....however, if the specs on new egg are correct....this board has

PCI Express 2.0 x16 3 (@ x16/x16/x4 mode)

If newegg is wrong......and it is in fact pushed to x8 x8, then I'd move up to a better board....if you're willing to spend $725 for the 5970, this shouldn't be that much of an issue after selling your SE.
March 28, 2010 9:50:07 PM

I know that my mobo supports x16 but something is wrong. I only have 1 5870 in the top blue slot but it's only performing at x8. Must be either a problem with the mobo it's self or my GPU. I have tried reseating it multiple times, cleaning the gold connectors and blowing compressed air in the PCI Express slot, nothing changes. I am happy with the P6T SE so I would only want to change if a 5970 was not working correctly. I have a fairly decent OC on my i7 so getting another mobo really won't change much.

I guess I will have to try find another PC I can test my 5870 in, if it still shows as running at x8 I know it's not the mobo. So if it was the card and I bought a 5970...would it work with the 5870 running at x8 and the 5970 running at x16?

Thanks for the reply.
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March 30, 2010 2:11:28 PM

Sorry to dredge up this thread again but I am still stuck at deciding what I should do. The 5870 I have must be damaged and that it why it's only running at x8 pci express instead of x16. If I was to get the 5970 for trifire I believe this would cause complications. So my idea is to buy 2 more 5870 cards and put the defective 5870 in the slower pci express lane (white bottom slot on P6T SE) Would that work out? Running 3 cards lowers the pci express bandwidth anyway does it not?

I still don't understand what would make a card run at x8 anyway. I know the card is still alright at x8 but it's still annoying that it's not running at spec. I just want to know if buying 2 more cards to work with my defective 5870 will cause less of a problem than buying a 5970 to go with it? Would a 5970 at x16 and my 5870 at x8 work? Thanks for reading.

a b U Graphics card
March 30, 2010 3:26:58 PM

I wouldn't think it was the Graphics card on this one but you never know. Did you update the bios on the MB or even reflash it? What was the other MB you put it on?
March 30, 2010 3:36:19 PM

I did not try the card in another motherboard but I put an 8800GT in this mobo and it was running at x16 as it should. That must mean it is the card. I have tried many many things to correct the issue including cleaning the card's gold connectors and the motherboard slot...even flashing the card's bios to various others. I forgot to try flashing the mobo again so maybe I should try that. Thanks for the tip. I already have the latest so I will try and flash the same one I have already.
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