how do you install a second gpu in quad sli?

aivas47 - thanks for the reply and clearing up my misconception. what i am actually after is what it take to run dual video cards in sli and you answered my question. so i just need a sli bridge? that sounds pretty easy.

Your signature says you currently have a 7900GTX card.  Adding a second one of those will let you run regular SLI (two GPUs), not quad.  All you need is a second 7900GTX card and an SLI bridge that connects the two cards inside the machine.  Dell Parts can sell you the second card and bridge as a kit I believe, or the bridge alone if you buy the card somewhere else.

 

For quad SLI you would need to pull out your 7900GTX and put in two of the 7950GX2 cards.  Each of those cards contains two GPUs, so you have four in total when they are linked with an SLI bridge.

The bridge is like a $25 part, something in that range.  At first Dell did not sell the bridge standalone, you had to go to one of the online computer part shops, but I've seen posts here fairly recently indicating Dell does sell the bridge now (sorry I'm too lazy to actually look up the part number).  It just snaps in place to connect the cards and away you go.  When you boot up after installing the second card and bridge the driver software will usually detect the SLI capability automatically and give you a pop up balloon, just click on that and it will take you to a screen where you check a box to enable SLI, and that's it.  If for some reason you don't get the popup you can still just go into the driver control panel and there will be a new option for SLI.

thanks for the help aivas47!

chris m - thanks for the reply!