Multi-GPU issues on single board

[djeZo]

Hello!

I have GA-Z77X-UD3H mobo and recently been running on 5 vid cards: 5870, 6870, 7850, 7950 and R9 280X. This combination worked fine. I was going to replace the bottom ones (5870 and 6870) with 7950 and 7970 in dual PSU setup but issues started to appear. All five cards were recognized, but in Windows (7, 64bit), R9 280X was disabled - error code 43. As soon as I took one of vid cards out of the setup, R9 280X had no such issue anymore. It also happened that some other card was disabled in same way - it looked like the system is f*cking with me with random errors. I also tried various drivers, searched google (really hard to find any good topics about 5+ gpu setups), tried with single PSU - nothing worked! All of the cards except one are connected to the mobo via powered PCIe risers. Due to bad design (pcie x1 close to pcie x16), I had to use x1 riser on primary pcie slot - I used non-powered here, since I assume that this slot provides enough power.

Today I also went through manual of the mobo and found interesting connector which is SATA power connector and should be powered if 2 or more vid cards are hooked with the board. Unfortunately, I cannot test this because the rig is not near me. Could this be the issue? R9 280X is connected to the last PCIe x1 slot and has own power via powered pcie riser. But maybe this extra power is needed for chipset and without it, chipset cannot function properly. But then again, why did my first setup with slower vid cards work fine?

Any ideas would be appreciated. Thanks!

[pjviitas]

You have provided a lot of information here.

In any event, I was messing around with multiple PSU setup and will relay what I learned.

Troubleshoot your GPUs first by switching them out of the pci-e 16x slot one at a time.

I am assuming all your powered risers work so there is no point in checking those.

Finally, I simply could not get multiple PSUs to work.  I would suggest a single PSU...sounds like you need around 1800W.

From all the reading I have been doing about multiple PSUs the problem seems to be one of the following:
1. Power feedback cycles between the PSUs
2. GPUs and PSUs not synched at power up.

Hope this helps.

[djeZo]

I don't believe the issue is PSU, because there is same problem when using only single PSU (which is enermax rev. 1250W and I suspect should be capable of at least booting them all up).

I am more interested into what can possibly cause Windows to disable device with error code 43. Are these chipset issues or power supply issues or driver issues?