Originally Posted by thisjustanother
what are some psu's you would recommend for running dual 7990s. and for anyone asking of motherboard, its the MSI z87 g45.
I have been running two 7990s in crossfire for several months now. Originally, with my old QX9650 CPU (Core 2 Quad) on an DFI X48 motherboard, and now, with my new Core i7-4930K on an Asus Rampage IV Extreme motherboard. Under water cooling, these cards are beasts and they shred everything I can throw at them.
The 7990s are power hungry video cards because of the dual GPUs. You are going to need a bare minimum of a 1200 watt, single rail power supply like a Corsair AX1200 or 1200i if you plan to overclock the CPU but leave the video cards at or below the default maximum frequency (1100MHz) allowed by AMDs drivers. Even then, you can trip these PSU's protection circuitry if you run a power supply torture test like the one in OCCT. The same goes for the torture test in Furmark. Yes, they can draw that much power. I know because I've done it.
If you purchase a multiple-rail power supply, then make sure that each card has a rail all to itself and that the rail is rated to at least 30 amps @ 12 volts. My current system uses a Lepa G1600 PSU (1600 watts). It's a great PSU, however, I had to carefully assign what was plugged-in to where in the unit because, when overclocked, a single 7990 can draw too much power from a single rail. If I overclock them using MSI Afterburner ( > 1100Mhz) and overclock the CPU as well, I can bring down the PSU using the Furmark torture test. It's not that the total rating of the PSU is being exceeded, but that the way the rails are divided up, the 7990 sucks too much power from the single rail. My overclocking of the 7990s above 1100MHz has been limited by this.
I am planning to switch over to dual Corsair AX1200 PSUs to see how far I can push the 7990s.
[EDIT: I'll be using Corsair AX1200s because I already have two of them from previous builds.]
BTW - The Lepa G1600 has no problems handling four, overclocked single GPU cards because the load can be better distributed among the available rails.Edited by Escovado - 11/16/13 at 6:59am