PSU and SLI GTX 560s

July 17, 2012 at 09:12:07
Specs: Windows 7, i5-2500k 4GHz / 16gb DDR3

I have just decided to get a second graphics card in my PC and go SLI. I just got my tax refund, so why not.

Both cards are a GTX 560 Overclock Edition -

However, I am having some trouble in getting the power working. My PSU is a fairly old (2009) Antec 750W.

The problem lies in powering number 2 card. I am using 2 of these cables (unfamiliar with the terms of power) plugged into the red slots in the PSU. When I press the power button on my case, all the fans twitch about half a turn, then everything just stays dead.

What have I tried?
Tried running just the new graphics card in pcie slot 1 with the original power cables. Boots up fine.
Swapped the cables to the 2 I plugged in. Dead.
Swapped card back to my old one on the new cables. Dead.

Whats happening? My thoughts would say that there is something shorting between the PSU and the cables and it wont run it.

See More: PSU and SLI GTX 560s

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July 17, 2012 at 20:18:33
Post your motherboard make and model.
Post the specs on your power supply, especially the Amperage on the 12Volt rail(s).
Are you trying to run the graphics off of the 2nd PCIe 16x slot with the 1st slot empty or unpowered? I suspect if this is the case, your motherboard/BIOS either does not support this or only supports video from the 2nd PCIe 16x slot then the first is powered and active, or your BIOS needs to be reset in order to run your graphics off of the 2bd slot or SLI mode needs to be activated (if available).
Your 750 Watt power supply may not have the amperage (or available wattage) on the 12 Volt Rail to power both of your cards together, especially if a lot of the higher wattage is available through the 5Volt or 3.3Volt rails which you cannot use. A common way to inflate the general Wattage numbers is to increase the available power to the 5Volt and 3.3Volt rails because doing so is much cheaper, but much of this is unusable power since most of the high draw components use the 12Volt rail for most of their power requirements.

You have to be a little bit crazy to keep you from going insane.

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July 19, 2012 at 07:50:40
Thanks, like a said, I dont know much about power supplies, so I got this off the side, hope you can decipher it for me.

My Motherboard is a Gigabyte GA-Z68XP-UD3R

On single card tests they have only been in the first pcie slot, I assumed having the first slot empty and unpowered wouldnt be a great idea.

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