I have a GA-Z68A-D3H-B3 Gigabyte mobo and was wondering about Sli'ing GTX 580's in the future.(i already have one evga gtx 580.) I noticed it has a PCI-Express x16 slot, a PCI-Express x8 slot and a PCI-Express x4 slot. Gigabyte claims this motherboard can sli and crossfire graphics cards. Do you need two x16 slots or can one be on the x16 slot and the other on the x8 or x4 slot. Any help would be appreciated.
On that board if you install 2 x gtx 580s, the bandwidth will be scaled to x8 for both cards. Which sounds bad, but there are varying arguments as to how much this effects FPS in real terms. Actual performance loss from GPUs running at x8 on the z68 /p67 platform is relatively small. So long as your PCI-E slot isn't scaled to x4 your looking pretty good.
Any time you put two card in sli or crossfirex, the lowest slot will make the PCIe x16 become PCIe x8 so now both card are at PCIe x 8. Now if you were to put one in the x16 slot and the other on the x4 slot then both cards will become x4.
You have the exact MOBO as I do and I will bet your PSU is also the same. As I have been learning about things I do know that the xtream gear 800w isn't good It is peak power and what you need is constant power and a brand name of Antec, Seasonic, XFX, and Corsair.
I have two GTX 550 Ti's and that PSU can handle that and I have my CPU OC'd to 3.9Ghz and I know I can go higher but my PSU would start to strain if I did that. You need to get a better PSU if you are going to add another 580. Here is a calculator so you can plug the numbers in and it will tell you what size your PSU needs to be. My next PSU is going to be 1000w.
These two calculators one easy one more complexed. I hope these help
I've read somewhere else on this website that you can run two 580's with an 800w psu as long as you don't overclock anything. Perhaps I will get a nice 950w psu when/if I get another gtx 580. I probbably won't be doing that until early next year. I am sure prices will go down once the 600 series have been released.
You are right the min is 800w. 600w is for one card then add about 200w more. The PSU has to be constant power not peak. If your 800w is in the brands I stated then you might be ok but if you have the xtrem gear then it won't cut it. Anyway just trying to help and I wish you good luck in futrue.