View Full Version : Adding a second video card to G5

Oct 4, 2009, 05:23 PM
Hi, I've got a G5 quad with the pci-e slots. I've got an Nvidia GeForce 7800GT already in the machine, and just picked up an ATI Radeon x1900 Mac edition to run a couple more monitors. The problem I'm running into is how do I supply power to the second card since the only 6 pin pcie connector I can find on the mainboard is going to the 1st video card? Does a splitter exist, or if I spliced two cables together would enough amperage be supplied? Both cards run off of a mini 6 pin pcie to standard 6 pin pcie cable. Any help would be much appreciated. Thanks!


P.S. This may be a crazy alternative, but I've got a pc I always run right alongside the mac that has a couple extra pcie power connections available. Could I run a power cable out of the pc and connect it to the Radeon card in the G5?

I saw an older thread where about midway down someone mentions successfully adding a radeon 1900 as a second card in the G5, but it never mentions the power connections. http://forums.macrumors.com/showthread.php?t=436693

Oct 4, 2009, 05:39 PM
ACTUALLY, do you use the optical drive very much? If not, then I'm pretty sure you can use the same solution people here have with dual 4870s - a PSU for the optical bay.

Something like this. (http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=2700091&CatId=1077)

Bad news is that it would most likely dump all the hot air into the case - I would get a fan-control program and up the airflow through the HDDs. That and it needs a plug - tacky way is through the front of the case, you might be able to get it through the rear if you don't have too many expansion cards.

And putting the card in slot 3 is your best bet :)

Oct 4, 2009, 08:37 PM
Thanks for the reply! After you mentioned the cd drive, I decided to take it out and attach two splitters together on the end of the 4 pin molex that's normally attached to the drive (one four pin to two four pin molex attached to two molex (each 3 pin) to 6 pin pcie). The guy at fry's said he's had success in the past with this although it's not generally recommended, but the connector that I used which is normally feeding the cd drive has 8 wires going to the 4 pin connector rather than 4, so I figured it couldn't hurt to try. Everything seems to be working great now, and I'm running a 32 inch lcd off the new card without any trouble. I even happen to have a spare usb cd/dvd drive that I'm now using to replace the optical drive I took out. Thanks again for the tip.


Oct 4, 2009, 09:39 PM

Oct 4, 2009, 11:42 PM
Glad to hear about your success.

I was actually going to recommend the PCIe from Molex first, as I've done it in a few PeeCees, but I wasn't too sure about the G5 and the power requirements for the card :o Shows how much I know.

Although DVD burning and data transfer on USB will be sl-o-o-o-w, it should be fine for the likes of DVD movies and etc. (I know from experience, my SuperDrive was external for a good amount of time)