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PCB Design and Cooling System

Like the first card in this review, the Gigabyte GeForce 7900 GTX is an exact copy of the reference card.


There are even fewer discrepancies here. The only things that indicate this is a Gigabyte product are a sticker with the company logo on the fan and an elastic cap on the MIO connector. There’s also a sticker with the card model name near the PCI Express x16 slot, but it is not easily seen due to the massive cooler. The cooler’s casing bears two halves of the Nvidia logotype although Gigabyte could have placed an original picture there like they did with their Gigabyte Radeon X1900 XTX.

Besides the ordinary stickers with serial numbers, there’s one with the version of the BIOS employed by the card. This information may be useful in some situations. The Nvidia GeForce 7900 GTX’s reference cooler is very light, especially in comparison with the Radeon X1900 XTX’s, and is fastened to the PCB with 9 screws without a back-plate.

The Gigabyte GeForce 7900 GTX uses the same memory as the Gigabyte Radeon X1900 XTX: Samsung’s K4J52324QC-BJ11 chips in 136-pin FBGA packaging. The memory is clocked at 800 (1600) MHz, exactly as described in the GeForce 7900 GTX specification. The chips having a capacity of 512Mb each, the total of graphics memory is 512 megabytes. These memory chips have a very low access time, so there is some reserve for overclocking. We are going to check how big it is in one of the following sections.

The GPU frequency complies with Nvidia’s specs, equaling 650MHz. This is the frequency of the pixel processors and raster operators (ROPs), while the vertex processors are clocked at 700MHz. The card uses traditional thermal interfaces: dense dark-gray thermal paste between the GPU die and the cooler’s sole and non-organic fiber pads soaked in thermal paste between the memory chips and the cooler’s base.

The Gigabyte GeForce 7900 GTX uses a copy of the reference cooler which was first employed in Nvidia Quadro FX 5400 and won our praises for its near-silent operation. The secret of this cooler is that its 80mm works at a very low speed, about 1000rpm. Here’s how this cooler works: the copper base takes the heat from the GPU and transfers it to the two heatsinks on the right and left of the fan via four heat pipes. The heatsinks are covered under an air-directing casing.

Some of the hot air is exhausted out of the case through the slits in the graphics card’s mounting bracket. Some air makes its way back into the system case.

This cooler does its job well, but is not free from drawbacks. The air stream created by the low-speed fan is very weak. As a result, the heatsinks and heat pipes become very hot when the card is in 3D mode, despite the low heat dissipation of the G71 chip. You may get your fingers scorched if you touch the heat pipes when the card is working, so be careful. This shouldn’t be a problem in a closed and well-ventilated system case.

There is a seat for a video-encoding Philips SAA7115 chip on the card, but the chip itself is missing, depriving the Gigabyte GeForce 7900 GTX of VIVO functionality. But as we’ve said in our earlier reviews, this feature isn’t very important for a today’s graphics card. Digitals cameras communicate with the PC via FireWire. And if you really need to capture analog video, you can buy a cheap internal or external TV-tuner that provides a number of additional features, too.

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