I want to run a p9x79 pro, 4820k, with 4 r9 290 cards. I know the mobo and cpu are overpowered for this, but I owned them before I decided to mine with them . . and mentioning them here helps me stress that I'd like to not destroy them. I want to use them to mine safely.
Anyways, I have a couple questions about using risers:
I will be using two different single rail 850w power supplies for this type of setup. If I mount them all on risers, do all 4 powered risers need to be powered through one PSU? If so, does it need to be the main psu that I'm using to power the mobo or the secondary psu powering only the two extra GPU's? If different, do the risers have to be on the same PSU as the GPU that is powered (2 risers on each PSU)? I intend to use the powered USB risers that have been linked here.
Alternatively, I already have a comp case . . so can I put two cards on the board in the case and two cards outside of the case on a stand? I'm asking this because I already built a stand that will hold 2 GPU's and the second power supply. I'd like to know if I should just put all 4 cards off the mobo and on the stand (I designed it to fit up to 4 cards, but only has supports for two right now) . . or if I can get away with 2 in the case and two out? If the split 2in 2out option is ok . . should I still have the two powered risers that I'll be using on the main PSU or the one outside the case? If this isnt safe I have no problems modifying my stand . . but it would be nice to save time if I can do it safely.
No all 4 risers do not need to be powered from the same supply. You can have one feeding the two in the case for the risers and the cards and another feeding the two on the stand and their risers