Overclocking The GeForce 7950 GX2

Although the GeForce 7950 GX2 is as large as the GeForce 7900 GTX, it actually consists of two cards joined together by a bridge connector. So, technically, it is a two card solution, even though it uses a single PCI Express slot.

To keep within its limited power and thermal envelopes, NVIDIA clocked the GeForce 7950 GPUs at a low speed of 500MHz. That's just 50MHz faster than the GeForce 7900 GT and 150MHz slower than the GeForce 7900 GTX. They probably undervolted it as well to keep the power consumption to a relatively low 143W.

But don't be fooled by the low numbers. This card gets very hot, even with extra cooling. It would be quite hard to keep it stable if your enclosure isn't properly ventilated. This will be a problem for those who live in the tropics.

Therefore, we added an extra 120mm fan to the system. This allowed us to achieve stable overclocks with no visible thermal throttling. There were minor visual artifacts though.

The fan was placed next to the card, providing fresh air from outside the case to the card's own fan. It also flushed away the hot air from the cooler and provided additional cooling to the card.

Overclocking the GeForce 7950 GX2 is really not a big issue since it is really the same G71 core used in the GeForce 7900 series. This core has been proven to be able to hit 650MHz with ease.

In the end though, we were able to overclock the GeForce 7950 GX2 to a maximum stable core clock speed of 600MHz and a memory clock speed of 780MHz. Therefore, when fully overclocked, the GPUs were 100MHz or 20% faster and the memory chips were 180MHz or 30% faster.

That was probably the best that this card could do with its puny coolers. Unfortunately, it's not possible to use any good third-party coolers with this card. It is certainly even more impossible for extreme overclockers to try a banzai attempt with liquid nitrogen or phase-change cooling.

Well, the word "impossible" is probably the wrong choice of word since nothing can stop them from pulling crazy stunts! But the limited space they have to work with will limit their options and make it harder to do anything. Still, if anyone wishes to give it a try, we wish them the best of luck!

Quad SLI

Since the GeForce 7950 GX2 is essentially two cards in SLI mode, pairing two of these cards makes it a Quad SLI solution. However, it's not as easy as it sounds.

For one thing, you need to use a driver that supports Quad SLI with the GeForce 7950 GX2. As far as we know, NVIDIA has declined to release this driver publicly. They did say that it will be released in the future. So, keep your fingers crossed!

Since the GeForce 7950 GX2 was clocked as low as the GeForce 7900 GT it was no surprise that the 480W Antec TruePower II power supply we used in our testbed had no problem handling the load. But it was a totally different story when it came to Quad SLI.

The 480W Antec power supply, which was capable of up to 18A on the 12V rail, could not handle the load and actually shut down. We had to source for a more powerful power supply. The best we could come up with, at such short notice, was a 550W Acbel power supply, capable of 22A on the 12V rail.

Fortunately, it worked. The extra 4A was enough for us to run an extra GeForce 7950 GX2 card. So, if you are interested in running two GeForce 7950 GX2 cards in SLI, be sure to get a power supply that supports at least 22A on the 12V rail. We recommend a higher capacity power supply, of course.

On no occasion should you go for lower quality power supplies, even those with stupendously high ratings. Always check the rating of the 12V rail. Lower quality power supplies often load the majority of the power on the 5V rail.

Now, let's go find out just how fast this card is!