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PCB Design

Nvidia doesn’t watch so intently that the manufacturers stick to the reference design in mainstream products as it does with regards to top-end GeForce 7900 series cards, so there are some unique designs available on the market. The Gigabyte GV-NX76T256D-RH “Silent Pipe II” is among them. The GeForce 7600 GPU series requires a very simple PCB thanks to a 128-bit memory bus and low power consumption and any advanced graphics card manufacturer, especially such a giant as Gigabyte, can take up the job of designing and releasing such a card. So, we won’t talk about differences from the reference GeForce 7600 GT because the Gigabyte card has a completely new PCB design developed from scratch.

There’s not the least similarity here, from the color of the lacquer the PCB is coated with to the power circuit design and the placement of the memory chips. The cards only have the DVI/S-Video outputs and the MIO connector (it connects two cards in a SLI tandem) positioned in exactly the same way.

The power circuit of the Gigabyte card is considerably simpler than the reference card’s. It uses fewer electrolytic capacitors, MOSFETs and case-less coils, yet its heart is still the same pair of Intersil ISL6594 controllers located on the reverse side of the PCB. With a peak consumption of 35-37W, the certain simplification of the power circuit shouldn’t affect the stability of the device. The elements are all neatly assembled, except for the 60T03GH MOSFET in the bottom right corner of the PCB which doesn’t stand upright for some reason.

In the top left corner of the card, near the MIO connector that is covered with a plastic cap, there is a seat for a 4-pin connector like those that are used on sound cards to attach TV tuners or CD/DVD drivers, but the connector itself is missing on our sample of the Gigabyte GV-NX76T256D-RH. The same connector used to be installed on ATI’s Radeon X800/X850 cards to attach a video input located on the front panel of the PC case. The PCB developed by Gigabyte engineers doesn’t have a place for a VIVO chip, so this connector must be intended to provide a video output in any place of the case as is convenient for the user. The lack of VIVO functionality is not regrettable at all in this graphics card, even though it is positioned as a solution for home multimedia entertainment centers. Such centers are always equipped with TV-tuners which, besides their main purpose of reproducing TV channels, allow connecting to analog video sources. The quality of video capturing is generally higher with TV-tuners than with graphics cards that offer VIVO functionality due to the use of better media processors. Besides that, some advanced TV-tuners provide the option of hardware compression of the captured video signal into MPEG-2 or even MPEG-4 format which is unavailable on simple and cheap VIVO chips that some graphics cards are equipped with.

The memory chips are rotated by 90 degrees in comparison with the reference GeForce 7600 GT. Their shorter side is now parallel to the GPU package sides. Unlike an overwhelming majority of graphics cards tested in our labs, this device employs graphics memory from Infineon rather than from Samsung. The four chips in 136-pin FBGA packaging are marked as HYB18H512321AF-14. This is GDDR3 memory. Each chip has a capacity of 512Mb, is designed as 16Mx32, and works at 2.0V voltage.

The “-14” suffix denotes an access time of 1.4 nanoseconds and, accordingly, a rated frequency of 700 (1400) MHz. The memory chips are indeed clocked at this frequency, in full compliance with the official GeForce 7600 GT specification. Organized as 16Mx32, four such chips provide 256 megabytes of memory accessed across a 128-bit memory bus. We’ll check out soon how good this memory is at overclocking.

Notwithstanding the passive cooler, the graphics processor of the GV-NX76T256D-RH card is clocked at 560MHz, exactly as in the official GeForce 7600 GT specification. This shouldn’t become a problem considering the low heat dissipation of the chip and the design peculiarities of the Silent Pipe II cooler. However, we wouldn’t recommend using this card in a poorly ventilated system case, which is in fact a general recommendation for any passively cooled graphics card.

 
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