Bitcoin Forum

I have 4 Asus R9 280x GPUs and I can only seem to get two of them running. Both green lights and both fans are working on all the cards except Windows and CGminer is only detecting 2 cards.
They're connected to a Asus P8Z68-V LX motherboard with PCI-e 1x powered risers.
I've changed the BIOS settings to allow the 1x slots to be active.
Would the installation of jumper cables on the 1x slots be necessary?
As described here:
http://www.gobitgo.com/articles/1001/How-To-Correctly-Use-and-Install-PCI-E-Riser-Cables/

Other specs include i5 2500k, 8GB Corsair RAM and Dual PSUs.

Thanks in advance!

Buy a bigger power supply

I don't think that's the problem. I have 750W+850W. The 850W was enough to power the whole system when I only had 2 cards and the TDP of the R9 280x is 358W I think, so I should be fine with what I have.

If no-one else can help I'll have to try installing the jumper cables on the PCIe x1 slots and hoping for the best!

Many times the power supply deliver less than they should deliver, try to do a test with a 1000 or 1200 PSU

I don't have a 1000+W PSU just laying about I am afraid...

It's a problem with the x1 lanes/riser combination. I'm pretty sure I need to put in jumper cables, I was just wondering if anyone could advise me further?

I'm pretty sure it will work with a jumper wire in the two slots that aren't working :).
They really aren't difficult to make and install, so the best would be to just try them first.
I'm sure you won't need any help since that article does explain a lot (there are also a lot of other articles out there), but if you do, don't hesitate to ask.

Have you tried swapping the non-detected cards for the detected cards to make sure that all 4 cards do work.

Then you should also check the 1x risers. They could be not working.

I don't think its a PSU problem because you do have enough power. All PSUs have a power efficiecy rating(Gold,Silver,Bronze,etc) so if your efficiency is 85% and its a 1000W PSU, then it will only be able to handle 850W max.

Cheers guys!

All 4 cards and all 4 risers work when plugged into the x16 slots so I am going to try the jumper cables. Wish me luck!

Nope. Still not working!

I've tested all the cards and risers individually and they're all fine.
I've hooked up each power supply to a card on the x16 lane and the x1 lane - only the x16s work.
I've changed the Mobo BIOS to allow use of the x1 lanes.
I've installed jumpers onto the x1 lanes.

Only the cards connected to the graphics card slots are working.

What am I missing here?

PLEASE HELP ME!

Are you sure? I thought that was the efficiency of the conversion from AC to DC. So it would be drawing 1000W but only giving a usable output of 850W. A review of my 850W PSU said it was capable of putting out well over 920W before it died.

I insist,  try PSU 50% bigger than what you think is necessary.

It might be that your MB doesn't accept all the pci-e slots working at the same time. I have the typical Z77 G45, and somewhere in the manual says that if I put some cable in pcie number 3, the pcie number 4 will not work (I don't remember the details but it goes along those lines).

Another problem I'm thinking is that the PSU's are not well hooked up together, I'm about to receive my second PSU and I'm planning to connect them together with http://www.add2psu.com/, although I wouldn't know why using one PSU only for the PCIE 6+2 pins (for the extra two graphics card) wouldn't work. But I'm just makng sure.
And I think you do have enough power, unless you are OC like crazy.

I can't really afford to buy another, larger PSU at the moment. If all else fails I might have to buy or borrow another motherboard as I have all the other components I require to build another dual-card rig.
Or, can anyone recommend a cheap 1155 motherboard that will definitely accept 4 GPUs?

Just another bit of information about my setup; the risers and the PSU connectors were purchased from here:
http://litecoinminingparts.com/shop/

According to ASUS, "The PCIe x16_2 slot shares bandwidth with PCIe x1_1 slot, PCIe x1_2 slot." But if I am just using these cards for mining the slightly limited bandwidth wont matter, right?

Up to 6 GPU's
http://www.amazon.com/MSI-Computer-Corp-Motherboards-Z77A-G45/dp/B007QWI9TY/ref=sr_1_1?ie=UTF8&qid=1391625041&sr=8-1&keywords=z77a-g45

Don't worry about the bandwidth