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PCB Design and Specifications

Every GeForce 9800 GTX selling today uses the reference PCB design. They are all manufactured on contracted facilities and sent ready-made to Nvidia’s partners. Modifications are not yet allowed but the GeForce 9800 GTX is far simpler than the GeForce 8800 GTX/Ultra and we have no doubt this graphics card will appear with nonstandard PCB designs sooner or later. The Zotac card is a copy of the reference sample, differing from it with the stickers on the cooler’s casing and fan.

Despite its 256-bit memory bus that simplifies PCB wiring, the GeForce 9800 GTX is as long as 27 centimeters or as the GeForce 8800 GTX. Consequently, this card is incompatible with a number of system cases, not only with compact barebone or microATX but also with ATX cases that have a shortened design or a specific position of the HDD cage.

The power circuit is quite complex for a G92-based solution. The four-phase GPU voltage regulator is based on a Primarion PX3544 controller. The two-phase memory voltage regulator is based on an Anpec APW7066. The card has two PCI Express 1.0 plugs for connecting external power although this is not really necessary: the combined load on these connectors is but slightly above 60W, which is far below the load capacity of one connector (75W). However, you have to use both connectors for the card to start up and work. Zotac included appropriate adapters for people whose PSU has only one 6-pin power connector or no such connectors at all.

There are eight memory chips on board (Samsung K4J52324QE-BJ08, 512Mb, 16MB x 32). These are the fastest GDDR3 chips available today. They have a rated frequency of 1200 (2400) MHz at 1.9V voltage. The memory frequency is increased over that of the reference GeForce 9800 GTX: 1152 (2304) MHz against 1100 (2200) MHz. The memory bandwidth is increased from 70.4MBps to 73.6GBps as the consequence. It is not as high as the memory bandwidth of the GeForce 8800 GTX (86.4GBps), let alone GeForce 8800 Ultra (103.7GBps) but the G92’s memory controller is more efficient. It is the amount of graphics memory rather than its bandwidth that may sooner become a bottleneck. Unfortunately, the GeForce 9800 GTX carries only 512 megabytes of memory on board and this may be not enough for some applications especially as Nvidia’s current-generation GPUs are known to suffer from inefficient memory management. So, if you own a GeForce 8800 Ultra and play games at high resolutions, you should not hurry to replace your card with a GeForce 9800 GTX, even pre-overclocked.

The GPU installed on the Zotac GeForce 9800 GTX AMP! is marked as G92-420-A2 and has a standard configuration with 128 unified stream processors, 32 (64) TMUs, and 16 raster operators grouped into four sections with four 64-bit memory controllers. The main GPU domain is clocked at 756MHz while the shader domain is clocked at 1890MHz. Being far higher than the reference ones (675MHz and 1688MHz respectively), these frequencies should ensure a larger performance gap from the GeForce 8800 GTS 512MB.

As opposed to the GeForce 8800 GTS 512MB, the Zotac is equipped with two MIO connectors to support Triple-SLI configurations. Besides, the card offers two dual-link DVI-I ports (with support of HDMI/HDCP and resolutions up to 2560x1600 inclusive) and a standard 7-pin mini-DIN connector for analog video output in Composite, S-Video and YPbPr formats. The audio-over-HDMI feature is supported by connecting the graphics card to an internal S/PDIF output of the sound card using the included cable.

The card is cooled by a standard reference cooler from Nvidia whose origin goes back to the GeForce 8800 GTX. The cooler consists of an aluminum frame on which a large composite heatsink, made up of thin aluminum plates, is installed. Heat pipes connect the heatsink with the copper heat-spreader that contacts with the GPU die. The heat pipes are placed in such a way as to distribute the heat uniformly in the heatsink. There is a layer of dark-gray thermal paste between the cooler and the GPU. The memory chips and power elements transfer the heat to the aluminum frame via fabric pads socked in white thermal grease.

A Delta BFB1012L blower is installed at the back of the cooler. There are slits in the card’s mounting bracket for the hot air to be exhausted out of the system case. The whole arrangement is covered with a black plastic casing. The cooler is secured on the PCB with 14 spring-loaded screws and an X-shaped bracket. The casing is additionally fastened with three screws to prevent any misalignment.

Practice suggests that this cooling system design is optimal, combining high cooling performance with little noise. The cooler is going to cope easily even with the pre-overclocked version of GeForce 9800 GTX provided by Zotac.

 
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