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CrossFire does not work

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Hi all!

 

I have two identical Radeon HD 7870XT graphics cards, which were installed in PCI-EX16_1/2 slots on this motherboard in CrossFire configuration. Yet in motherboard BIOS, the link speed for one graphics card was x8 and link speed for the other was only x2. For CrossFire configuration to work, both graphics cards should work at the same speed.

 

These graphics cards worked flawlessly in CrossFire configuration on my old Asus P7P55D Pro motherboard right up to the moment I installed them on this new motherboard. I did everything what end-user would be expected to do to make it work: reseated graphics cards and switched their places, reseated CPU, cleared CMOS by removing and placing the battery back, updated motherboard's firmware, even changed graphics card connectors on my modular be-quiet Power Zone 850W power supply.

 

I returned this motherboard to retailer for replacement assuming there might be a problem with lower red PCI-E slot or with CPU socket and PCIX controller wasn't working correctly. The retailer claims their Asus support staff tested my motherboard with two nVidia GTX 780 cards in SLI and AMD Radeon 280 in CrossFire and that both PCI-E slots woked at x8 speed in the following setup (Intel Core i3-4130, 2x4GB G.Skill DDR3 1600Hz, Corsair TX850W, WD Green 2TB, Windows 8.1 x64).

 

What could be the reason my graphics cards do not work in sync? Could there be compatibility problem between my graphics cards and this particular motherboard? Would it help if I updated graphics cards' firmware. Where I could get newer version of their firmware and how I could do it?

 

My system:

Motherboard Asus Maximus VII Hero

Graphics cards Club 3D Radeon HD 7870XT (Tahiti LE)

Processor Intel Core i7-4790K

Memory 2x8GB Corsair Vengeance DDR3 1866MHz

Power supply be quiet! Power Zone 850W

Operating system Windows 7 Home Premium x64

Graphics cards and CPU are watercooled.

 

I would appreciate any help in solving this mystery.

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Have you tested each card by itself on the motherboard?

Not with this new motherboard. For some time I've only had one of those graphics cards on my old motherboard. Then I bought the second one and they were working fine right from the start. So in a way I have tested at least one of the cards by itself [on my old motherboard].

 

It's complicated to test each graphics card by itself because every time I have to drain the entire system and waste more than a liter of coolant. But so far I swapped their places twice and had the same result. I doubt any of the card is faulty. What else testing each card by itself could prove?

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So your only using the two Red Expansion slots for graphics cards, and not using any of your Black Expansion slots for anything, or M.2 slot.

 

That's vary strange if all other Expansion slots are empty you should be seeing X8 on both Red slots running dual cards.

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So your only using the two Red Expansion slots for graphics cards, and not using any of your Black Expansion slots for anything, or M.2 slot.

 

That's vary strange if all other Expansion slots are empty you should be seeing X8 on both Red slots running dual cards.

That is correct, I'm only using the two red expansion slots for graphics cards and not using ANY other expansion slots or M.2 slot.

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+1, it has to be a driver issue. The only other thing I can sugget is updating the bios, but if Asus support was able to run it just fine, I cant see that really causing this problem. Try uninstalling and wiping/cleaning  the drivers out befor reinstalling and see if that fixes the problem.

 

edit: it looks like both the Tahiti LE and Pitcairn XT chips where used on the 7870. Now they should work togther but maybe, once again it's a driver isuse casuing them not to work togther. Also which card was in the first slot on your old build? I definitely had a simliar issues years ago with the 4850 cards. It just would not work with one of the 2 cards in the first slot. The other worked fine and allowed xfire to work.

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Yesterday I did a clean [re]install of the entire operating system. ALL the latest BIOS, motherboard and AMD drivers are installed. I still don't get CrossFire tick box in Catalyst Control Center. GPU-Z utility also reports that CrossFire is disabled. I ran GPU-Z's PCI-Express Render Test. The primary card's slot configuration was PCI-Express x8 v.3.0 but the secondary card's slot configuration was only PCI-Express x2 v.1.1.

 

I already flipped the cards around on this new motherboard and the problem remains with second PCI-E slot, not with any particular card. I have another CrossFire bridge and tried it already. The PCI-E and CrossFire bridge connectors on both cards seem to be intact (I even cleaned them off possible oxidation, dirt or grease). The cards seem to be fully seated in the slots (locking mechanism is engaged on one side and cards are fixed to the case on the other).

 

By the way, both cards' BIOS versions, BIOS part number and BIOS date are the same. Physically the cards are identical copies of each other.

 

Am I running out of options here?

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Your not running out of options,.. but you are getting closer to figuring out what is causing issue,.. by confirming exactly what is not causing issue,..

 

You completely uninstalled all AMD software using catalyst install manager then uninstalled catalyst install manager, restarted PC and confirmed all files drivers etc are removed.

 

Then reinstalled Catalyst install manager Version : 08.00.0916,.. checked installation report "packages for install" final status : Success on all,.. and received No Error Messages in installation report.

 

 Windows Device Manager Display adapters shows "Two" AMD Radeon HD Cards, properties shows device is working properly, with Driver Version : 14.501.1003.0,.. 11/20/2014

 

When you open Catalyst Control Center, click Performance and then confirm AMD CrossfireX is Enabled, and in AMD Overdrive select the GPU to be configured: shows "Two" Radeon HD Series Cards.

 

And your still Not seeing X8 on both Cards,.. :wacko:

 

Asus Support tested your motherboard with i3 processor confirming lanes work at X8,..your running i7 processor are BIOS current,.. could be issue with your CPU or BIOS,.. have you removed processor checked pins and reseated.

 

I would need to test both cards in CF on different rig to confirm cards work at X8,.. do you have access to a test platform to confirm cards work in CF,.. if Cards work at X8 on test rig then your CPU or BIOS could be issue.

Edited by Braegnok

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braegnok, he reinstalled windows, so I think that would remove the old drivers.  And the problem isn't only that they don't run at x8 bus speed, but he can also NOT enable crossfire

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Precisely. And like I said before, both cards worked in CrossFire configuration on my old motherboard right before I installed them on this new motherboard, which proves that both ran at the same bus speed with the only exception that that motherboard has PCI Express 2.0 slots. I also built the system back up after I received this motherboard from retailer's Asus support. And I did check processor pins [again], which seemed fine to me. If there was anything wrong with pins, then Asus support would run into the same problem. And now the CPU and graphics cards reseated again. Before installing operating system for the very first time the first thing I did is updated BIOS to a new version. At some point and out of desperation I even reverted back to the old version that motherboard came with. But now I have the latest BIOS again. Can it be so that all versions of BIOS are so screwed up that they don't recognize 2-year old graphics cards?

 

Can CPU itself be faulty and how could I prove that? But again, this is brand new CPU right from the box. What are the chances that it's faulty?

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