Two GPU's. Only 1 works at a time

[Ryjohn]

I've just installed a second GTX 770 in my system, and have encountered an issue. Both cards are sat snug in the PCIE16 slots, and both are getting power, however, my system can only detect one at a time. When they are both plugged in, only the card in slot 1 is detected, yet when when I take out the card in slot 1, the card in slot 2 magically starts working. Can anyone suggest why this could be.

What I've tried:
-Using one card without the other
-Swapping the cards around
-Installing/uninstalling/reinstalling drivers
-Looking in BIOS for setting which might disable PCIE slots
-Trying it with/without the bridge

Hardware:
750W PSU
2x Geforce GTX 770 2GB
Asus P8Z77-V Pro Mobo


[SOLVED] So I pretty much ripped my PC apart and rebuilt it from the ground up and now everything is working fine. No idea why. But anyway, thanks to everyone who helped, all the internet points to you.

 

[xSamaru]

did you put on SLI bridge?

 

[Mike_Tech]

This has been covered by another member of the community before possibly try their solution to change the PCI-E mode to PCI-E 2.0:

http://www.tomshardware.co.uk/forum/387333-33-asus-p8z77-premium-gtx660tis-issue

Solution courtesy of jn2guru
http://www.tomshardware.co.uk/community/profile-1046781.htm

 

[Ryjohn]

This has been covered by another member of the community before possibly try their solution to change the PCI-E mode to PCI-E 2.0:

http://www.tomshardware.co.uk/forum/387333-33-asus-p8z77-premium-gtx660tis-issue

Solution courtesy of jn2guru
http://www.tomshardware.co.uk/community/profile-1046781.htm

I gave this a go , but its having no effect. The person you've referenced seems to have both cards detected, but the second is causing performance issues. My issue is that the device manager will only acknowledge that 1 card is present at a time. When I have both cards in, the card in slot 1 is detected. With card 1 removed, card 2 is suddenly detected with no changed being made to it by me

 

[Ryjohn]

did you put on SLI bridge?

I've tried with and without the bridge, no difference either way

 

[saywhut]

did you put on SLI bridge?

I've tried with and without the bridge, no difference either way

Are you able to flash the BIOS to see if there is any change?

 

[Ryjohn]

did you put on SLI bridge?

I've tried with and without the bridge, no difference either way

Are you able to flash the BIOS to see if there is any change?

I've checked in BIOS, it shows up the same as device manager, only the card in slot 1 is detected if they are both in, the second is only detetced if the card in 1 is out. The bridge seems to be doing very little atm.

 

[saywhut]

Latest BIOS is Version 2104, is that what you're running?

 

[Ryjohn]

Latest BIOS is Version 2104, is that what you're running?

Yep running 2104 now, still no change of the GPU side of tings

 

[saywhut]

Latest BIOS is Version 2104, is that what you're running?

Yep running 2104 now, still no change of the GPU side of tings

Do you have any other video card by chance to put in the second PCIe16 slot besides the secondary 770 just to see if it gets recognized with the primary 770?

 

[saywhut]

Also, the PSU jsut came to mind. What PSU do you have exactly? Look at
http://www.tomshardware.com/answers/id-2091648/gtx-770-sli-power-supply-requirements.html
for reference.

 

[Ryjohn]

Also, the PSU jsut came to mind. What PSU do you have exactly? Look at
http://www.tomshardware.com/answers/id-2091648/gtx-770-sli-power-supply-requirements.html
for reference.

I'm using a Corsair CXM 750W Modular, so I'm 90% sure there should be enough power floating around for both to run. And also, no, I'm afraid I haven't got any other cards. This is my first PC build, so I havn't got spares lieing around from past ventures into PC construction.