I had another thread open recently on much the same subject. Since then I've returned the second (faulty) GTX480 I'd bought, pulled out the original one too and bought 2 x Asus GTX580's instead. The problem is - and I think it's a PSU/power connector problem - the system won't boot. The Asus cards (it's not the Matrix, just the normal overclocked one @ 782 MHz, I think) have 2 x 8+8 PCIe connectors and my PSU only has 8+6 connectors. Hopefully that's the real problem and I can fix it by buying some modular cables.
The steps I followed are:
1. Install 2 x GTX580s and connect SLI bridge
2. Power up, all fans spin, the cards light up but no display & no POST (each of the 4 motherboard LEDs light up in turn - cpu, RAM, VGA, boot device (although the boot device stays on for about 10 seconds before fading))
3. The cpu fan spins at a lower speed than when the system is booting properly
4. Try every combination of card(s) in No. 1 & No. 2 PCIe slots
5. Put GTX480 back in (and it works)
My rig is:
Coolermaster HAF X
Coolermaster silent pro gold 1000W (modular)
i7-2600k @ 3.4GHz
Arctic Cooler Pro 13
8GB Corsair Vengeance CL8
OCZ Vertex 3 Max IOPS 120GB SSD (system)
WD 450GB Velociraptor
2 x Asus GTX580 SLI
Is this a simple case of not having the right power connectors? I'm assuming I can buy 2 8+8 cables for my modular psu.
The specs of your power supply say it has 4 x 6+2 pin connectors, which snap together to work just like 8-pin connectors. So you should have exactly enough to power your two cards. Are you sure you're not mistaking some of the 6+2 pin connectors for regular 6-pin connectors (which your PSU also has four of)?
Thanks for the replies.
The psu has 4 x 6+2's but they're on 4 separate cables, so each is paired with a 6-pin. I'm not sure if the 2 x 8-pin power connectors on each card are identical but I'll take a closer look at it (and the adapter in the box) when I get home. I may be able to use 2 separate cables for each card.