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PCB Design and Cooling System

As opposed to the above-described solution from Gigabyte, this graphics card is based on the reference design. It’s expectable since Foxconn is Nvidia’s main partner in manufacturing graphics cards.

The only difference you can spot with your eye is the lack of screening on the DVI-I connectors. Otherwise, the card from Foxconn is to the smallest detail identical to the reference one. The reference PCB design proved to be so successful that as many as three GeForce 7 models were based on it: GeForce 7900 GT, GeForce 7900 GS, and GeForce 7950 GT.

Just like the Gigabyte GeForce 7950 GT, the Foxconn GeForce 7950 GT 256MB uses GDDR3 memory from Qimonda, but its HYB18H256321AF-14 chips have a capacity of only 256Mb each, providing a total of 256 megabytes of graphics memory. The rest of the parameters of the memory chips coincide. The memory is rated to work at 700 (1400) MHz, but is clocked at a somewhat higher frequency of 780 (1560) MHz. There’s little reserve left for overclocking left.

The GPU frequency is increased above that of the reference card and is set at 580MHz (600MHz for the vertex processors). This should give the Foxconn an edge over the ordinary GeForce 7950 GT in those situations when the amount of graphics memory is not important. Since we are going to check out the influence of the amount of memory on performance, we will benchmark both cards at the reference frequencies. Note also that Foxconn also offers a similar card but with 512 megabytes of onboard memory. It differs from the discussed model with the characters 3D2 in its name. The non-overclocked versions have a simpler cooling system and the suffix HP instead of HPOC.

The reference cooler is known to be able to cope with the GeForce 7900 GS or GT easily, but it finds it very difficult to cool the core of the GeForce 7950 GT which is clocked at 550MHz. The GPUs of the pre-overclocked versions of the GeForce 7950 GT offered by Foxconn have an even higher frequency, so the company decided to install a more advanced cooler on such cards.

This cooler looks simple at first sight: a copper heatsink covered with a casing and equipped with a rather large fan.

However, the cooler from Foxconn has a special feature that helps it cope with the increased thermal load. We dismantled the cooler to show that feature to you:

As you can see, there is a flat U-shaped heat pipe in the cooler’s base. This pipe transfers heat from the copper piece that contacts the GPU die to the heatsink. The photo shows that there is a layer of dark-gray thermal grease in between the copper piece and the GPU die.

By the way, the cooler’s base is made not of copper, but of anodized aluminum as can be seen in the places where the cooler is fastened to the PCB. The memory chips are not forgotten, which is a rare thing for GeForce 7900 GT/GS and GeForce 7950. Here, the GDDR3 memory chips have contact with the cooler’s base through four elastic thermal pads. Their heat conductivity is probably low, yet that’s enough to cool the memory chips. At least, this is anyway better than if the chips were left without any cooling at all in the heat bag under the bottom of the cooler. The cooler is fastened to the PCB with four spring-loaded screws. That’s enough to secure it firmly since the cooler is rather small. There’s no danger that the PCB would bend or the GPU would get damaged by the cooler.

The cooler’s fan has a diameter of 70 millimeters and a consumption current of 0.39A. These characteristics are superior to those of the original fan in Nvidia’s reference cooler. The fan uses a 2-wire connection. It may be noisy if the speed management system is set up too aggressively, but we’ll check this out in the next section. Speaking in general, the cooler Foxconn installs on its pre-overclocked models of the GeForce 7950 GT has no obvious drawbacks and looks superior to the reference one.

 
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