pcie slots

[darrenay]

don't know if this is the right place for this but i'll give it a go anyway, my problem is this, I have 2 r9 280x's when I install the first 1 everything is great, but when I put the second card in and enable x-fire the pc automatically shuts down, I thought I had a problem with 1 of the cards so it was rma'd but was found to be ok. when I test using unigine it will obviously only test 1 card, it used to recognise 2 but like I said rma'd and every time I try to get things working the second pcie slot is causing issues. when I first built the system I got both cards working but suffered with the screen jumping and shutting down the pc every so often, did some testing and I came to the conclusion it was a graphics card. each card put in the first pcie slot works flawlessly and I get great fps, do you guys think it could be an issue with the second pcie slot ?????
gigabyte GA_Z87X-UD4H
i7770k
16 gigs hyper-x 1600mhz
2 sapphire r9 280x 3gig cards

 

[SavageCupcake]

What power supply do you have??

 

[darrenay]

sorry, its a new corsair cx 750m, I used the power supply calculator from this site, and it and a lot of people have said it is plenty good enough. I also have the aux sata connector connected for the extra power for x-fire. when I had both cards working originally I was getting 200 plus fps on a bf3 server

 

[SavageCupcake]

Ah by the shutting down my first thought was not enough power. Are you on the latest drivers etc?

 

[darrenay]

yes tried the new drivers, even used the drivers on the cd that came with the cards. actually watching my screen now, it has started the jumping again, i'm pulling my hair out at the moment, this was the card that was sent back rma. the second card started jumping on rare occasions earlier surely it cant be a issue with both cards. it makes me think it must be the MB pcie, I am sure everything is set in the bios that needs to be set properly, I've checked over and over