Nvidia GTX295 Quad SLI

 
 

Using the Gigabyte EX58 UD5 motherboard, I managed to overclock the OC3D test rig i7 920 CPU to 4000MHz. This increases to 4200MHz during load (Turbo Technology) which should give the GPU’s adequate headroom and minimise any CPU bottlenecks. I say hopefully as we are talking about a serious amount of GPU power here.

The GPU’s would not clock as high together as they did when clocked alone, with a measly (in comparison) 651 MHz on the cores and 1202 on the memory being the maximum semi-stable clockspeeds I could reach. We could have flashed the BIOS to EVGA versions and then used ‘Precision’ to increase the GPU voltages over stock. This would have allowed the cards to clock in excess of 700MHz but as they are not owned by OC3D, I didn’t relish the thought of killing the cards, explaining to the editor and no doubt paying for replacements thereafter!

 

During testing, I had the hair brained idea of adding a further card to run PhysX on its own and leaving the Quad SLI setup to deal with the graphics. For this, I intended to use the fastest single GPU available in the form of the Nvidia GTX285. 
Vista picked up the GTX285 and installed drivers and sure enough it showed up under devices and the NVidia control panel. I duly set the 285 as the PhysX enabled card and ran a quick Vantage test. Everything worked a treat but even with the GTX295’s overclocked and the CPU running at 4200MHz, Vantage returned a relatively weak score of 32k, little more than when I ran the cards at stock.

Despite repeated tests it was clear that the system was slower with the GTX285 in-situ than without. This is most likely owed to the fact that when 3 cards are used on the UD5 two of the slots are reduced to 8x PCIe which then throttled the GTX295. So, taking the GTX285 out I ran another test and the score was back up to what you see below.
 

It was a shame we couldn’t breach the 40k mark but I am under no illusion that the cards are easily capable of that under the right conditions. With the voltage tweaks available under the EVGA banner, the extra MHz allowed would  certainly make a difference as the scaling we have seen this far with the raw grunt of the cards is nothing short of amazing.
 
No LOD bias or other ‘cheat’ tweaks we used to attain the Vantage score, just the overclocks applied to the card. I would like to have shown that adding a third card for PhysX was worthwhile but with the power of 2 GTX295’s there is really no benefit at all and in our case, it was actually detrimental to performance of the system. I never thought I would say adding a £300 GPU would not increase performance!

Call of Duty 4 saw some improvements at higher resolutions, thanks in part to the extra 400MHz  CPU clockspeed allowing the GTX295’s more breathing space. Interestingly though, at the lower resolution FPS test actually decreased on average! I still feel that the tremendous amount of raw GPU power was still being held back with our CPU but alas, 4.2GHz was all our poor i7 had to give.

 

 

 

Well that about wraps up the extended overclocking section. It would have been nice to have some pots and LN2/dry ice to push things to breaking point but that would give the reader an unrealistic view of what was easily attainable. Still, it would have been fun seeing the editors face while I attach hulks of copper to the £400 GTX295’s and pour liquid nitrogen in them.

Let’s move on to the conclusion where I explain the pro’s and cons of owning a GTX295 setup….