3rd GPU "adventure"

[3D_Now!!]

Hi everyone, just thought I'd share my recent experience adding a 3rd GPU to my box.

I previously had 2 AMD 7790s inside (with Asus Z87-A MB, 16GB ram and Vertex 4 SSD) which at first knocked out about 70k PPD. Then, after successive driver updates and presumably bette WUs, they now knock out 130k PPD. The MB has 2 8x PCI express 3.0 ports and also a spare 2x PCI express 2.0, which is a tad of a squeeze at the bottom of the motherboard, so I bought a PCI extender cable which is like a very wide PATA cable. I then acquired a AMD 280x from eBay for £128 (Sapphire Vapour X). Unfortunately the first issue was that one of the fans was damaged. So after taking apart the board and concluding it was fully FUBAR, I left it with the one fan above the main circuit and hoped. Luckily, with this card mounted in the spare slot vertically in the case (fractal design define r4) it has direct access to the side vent, so one fan is actually enough to keep it sub 60C even while folding!) the next issue was getting enough power to it. Luckily there was just enough cable to get the 2 8pin PCI power connectors to it, and to the other two 7790s). The 750W XFX black edition still silent even with all this load (which is a fantastic power supply btw, based on a seasonic underneath).

So my next issue was software. I had to delete the previous slots as they now didn't recognise any of the cards, so I uninstalled and reinstalled FaH, which then lead to another issue, the cards either didn't get to 100% utilised or the cpu, didn't wind down after loading the GPU. after playing around, the catalyst 14.9 drivers turned out to be the best (I noticed a drop in PPD with the omega drivers before anyway). This sounds easy but took a lot of faffing around to discover! The catalyst control centre actually identifies the 280x as deactivated, but luckily FaH still recognises it.

So eventually the cards all worked and now the box is heating up a small spare bedroom quite nicely. The two 7790s getting the same 130k PPD and the 280x getting up to 170k PPD on its own. So sometimes a tidy 300k PPD altogether. Which is quite cool considering in 2012 I had a nvidia 440GT doing 5k PPD and a PS3 doing 1200PPD before that. Furthermore, the 7790s with 896 stream units do better on the 9201 WUs than on the 1046x units, but the 280x with 2048 stream units is the other way round. I guess this is due to the larger number of atoms in the 1046x units.

The most surprising thing for me is that a big card actually folds well (99% utilised) from a 2x PCI 2.0 slot. Also, the box now pulls 388W from the wall. After successive pausing and unpausing of the slots, I have deduced that the 280x uses ~120W while folding, and the 7790s use ~65W, despite having 250W and 85W TDPs respectively. The machine while idle uses 88W and the 50W delta is a i5 4670k at 4Ghz running CERNs Atlas@home (only 2 instances for stability) so the cup is at about 70%.

I thought I'd share this as it was quite complex trying to get the 3rd card working but now I'm actually pretty chuffed with it despite a rocky start.

[PS3EdOlkkola]

That's the great thing about FAH, it encourages both persistence and creativity - and you certainly displayed both in spades getting your rig to work. Very nice job and congrats on getting everything sorted out and nicely functional. Going the route you went -- versus buying something already made -- provides an unequaled understanding of your system and builds a nice new gaggle of newly energized neurons. Well done!

[Trendle]

Hello, your post caught my eye because I was thinking of using a PCIe 2.0 x2 slot for a 280X, but I assume that you're running one of the 7790's on that particular one?

[3D_Now!!]

Hi Trendle,

I'm actually using the PCI 2.0 2x slot for the 280x and it is 98-99% utilised 24/7, getting anywhere from 150k ppd (p9201) to 170k ppd (p1046x).

It is on a PCI extender cable and slightly awkward to fit (it needs a dusting soon!). I would advise you to think about how you are going to get 2 8 pin PCI power cables to it first though. I ended up using a molex-8pin adaptor I think came with the card.

I found the 14.9 drivers to be the best for my configuration.

Furthermore, do not expect to be doing any gaming on this card as the narrow bus does affect this (and folding seems to be the only program that recognises the card.

If you get any issues let me know I'll tell you what I did to overcome it!

Good luck

Matt

[Trendle]

Very useful information, thanks a bunch for your response.


Take care,

Trendle