I have a system build on a EVGA X58 4-way Classified motherboard. A few months earlier I had 4 pieces of EVGA GTX580 GPU's on the motherboard. I had 3 of them in sli and the 4the GPU was used as Physics card. It worked without problems since the motherboard came on the market. It still works perfect. A few months ago I could buy 4 pieces of MSI GTX 980 OC cards with 4Gb memory. Every GPU is tested separately and works perfect. When I put 3 MSI GTX 980 on the mobo in sli and a GTX 580 for Physics the system works perfect. But when I change the GTX 580 for the 4the GTX 980 the system goes perfectly throug the bios post but Windows 7 wil not start. I can take every combination of 3 GTX 980 + GTX 580 for Physics and the system works perfect. But when I put the 4the GTX 980 in Windows 7 wil not start.