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I have a rig with 3 x R9 280x's ,a MSI 990fxa mobo,600 watt PSU and 750 watt PSU.

The 600 watt runs the Mobo, CPU and a single R9 280x.
The 750 watt runs the other 2 x R9 280x's.
The Rig boots up into BAMT and all the cards are picked up but when it starts mining the 2nd PSU and the 2 x R9 280x's cut out!
The rig works fine with a single R9 280x's on the 750 watt PSU.

Thanks for your help !

!Bullet!

What OS are you using? How much RAM do you have?

Have you swapped out the cards to see if it could be a faulty card causing the issues?

I am using BAMT with 2 GB Ram (I doubt the RAM has anything to do with it)
Both of the cards are fine i have tested both individually.

Not sure with BAMT, but with my first packed Rig (4x 290x, 1x 280x, Windows 8, cgminer) 4 GB of RAM would not cut it. I had to add another 4 GB stick for it to run all cards.

One psu is sending messages to the other telling it to send 0 power. 280 290 cards chew some power and pull from the pci-e also and this does not work when adding different types of psu
you need something like what antec has its an oc cable and the psu communicates with eachother to allow different sized antect psu to work in tandem. A simple molex joining green wires will not do the trick
if anyone wants to argue this then i will gladly pull up a barrage of posts about this subject from the overclocking community..you do not mix different types of psu especially on the new cards and new pci-e 3.0 boards! joining green wires and what not is only so the psu turn on together it does not and will never solve your psu sending conflicting messages to each other through the mobo to the psu connected to your extra cards

Are you sure? My different dual psu's and my 280x's and 290x's play nicely together.


https://i.imgur.com/9tGVo0J.jpg

Not a RAM issue just installed 6 GB

How are your psu's set up? Are you jumping the 750 or using a splitter? It sounds like the power is not cycling right if the psu cuts off. I am obviously not an expert, but I have built and maintained many rigs so I do have a little experience.

There is no communication going on between both PSUs. The external PSU powering the video card is jumped and is only sending voltage to the GPUs and pci express adapter. This does work, and I currently use this solution to power additional video cards and other peripherals. The only way 2 PSUs can equally share power load, and "communicate" with one another, is if they are both connected over that antec device you mentioned, or other multiple ATX PSU solutions.

No.

Using powered riser's like the ribbon riser type and dual PSU will cause a short, as the 2 currents meet when they shouldn't .

you will need the USB looking PCIe risers which work correctly with dual PSU as they are hardwired to accept power only from the molex and not draw from the board. Or ribbon risers with capacitor which draws power ONLY from the molex.

Again its the power from 2 separate currents meeting at the board.


I have 6 x R9 280X with the USB looking powered risers .

Seasonic 1250W powering 4 cards and PC ..
Corsair 750W power 2 cards

Each PSU powers its own molex on the risers and the corsair is locked in ON mode, via bridged the green and black wire on the 24pin molex.

:)


Again: using ribbon risers with molex cause a shutdown on the system, its been explained before about the 2 PSU current's mixing when they shouldnt. you could blow the board and cards, if this is your problem.


PS: If you're only running 3 cards just upgrade to a good single PSU a seasonic 1250W can handle 4 cards and the components of the PC with no issues. and you could under clock to save on W usage if your worried about that.

Im going to try one of my other 750 watts from a different rig maybe a faulty PSU?

This is what I do, and it does work :)
Also, for my Coolermaster V850 (seasonic) I have it jumpered without the ATX cables attached. So much easier to use without having to jumper the ATX cable. :)

2 X 750 watt works perfectly

Good to hear

Thanks everyone ! ;)

Can vouch for a potential misunderstanding here. . . the usb risers are great . . but if you hook them to your secondary psu that is powering cards as well . . they will/can still burn out.

Just ran them for about 2 weeks and i've got two dead psu's and 2 burned risers to prove for it.

Lucky, the mobo and gpu cards were fine.

If you keep seeing your gpus temps go to 511c and 0 fan speed . . you're hooked up wrong. Simple as that.

There's multiple configs you can try . . all risers to primary psu .. . all risers to secondary psu . . . or each riser connected to the same psu that the gpu card its connected to .. . . just cycle them until it's not faulting to 511c/0 rpm. When you see that you're shorting current between the psu's and will blow one or both out. It really is different psu to psu. Some platinum cert ones will handle this w/o a problem . . while some bronze cert ones need a diff config. Comes down to what psu you invested in really.

If you doubt this . . then look for what looks like something got spilled on any of the risers/mobo/gpu and you'll know you f'd up. If it still works then keep on. If not then buy a new one and move on.