There are currently two versions of the GeForce 8800 available for sale. The 8800 GTX is the high-end version of the 8800 series, and as of right now is also NVIDIA’s flagship product. A slightly downscaled version is also available in the form of the 8800 GTS. Certain features and characteristics have been cut to reduce the cost of the 8800 GTS. Nevertheless, it still brings all the improvements of the G80 architecture including DirectX 10 support along with a unified shader architecture.

NVIDIA will be launching new versions of the 8800 series before AMD releases the R600 in an attempt to counteract the future AMD competitor. This week, actually, NVIDIA has launched a 320 MB version of its GeForce 8800 GTS. All aspects of this video card, including PCB layout and cooling remains the same. The only major difference is that the total amount of memory has been halved. The release of this video card will effectively reduce the cost of enthusiast-level DirectX 10. We will most likely have a review of this video card posted within this week.

The following table are the characteristics while the GPUs are under SLI.

The G80 is the first NVIDIA unified shader architecture. In a unified shader architecture, there are no longer any conventional vertex shader and pixel shader units. Instead, they have all been replaced with general purpose floating-point processors, which NVIDIA likes to call unified stream processors. The stream processors are extremely flexible in terms of the tasks they can handle. They are able to process vertices, pixels, and geometry or physics. In short, a large variety of workloads can be assigned to them.

By using stream processors, NVIDIA hopes to improve the efficiency of its video cards. This is primarily because stream processors can be dynamically assigned to tasks depending on the scene at hand. For pixel shader-intensive scenes, more stream processors can be assigned to processing pixel data. If the scene is more vertex intensive, more stream processors can be assigned to vertex calculations. This method of processing data is a large improvement over the traditional GPU architecture in which there are a definite number of vertex shading units and pixel shading units.

The 8800 GTX has a total of 128 stream processors, all of which operate at a speed of 1,350 MHz. In the G80 architecture, stream processors operate at a frequency that is completely independent of the core clock. For example, the GeForce 8800 GTX has a core frequency of 575 MHz. The stream processors do not run calculations at these speeds but instead at their own independent 1,350 MHz. On the other hand, texture filtering units, which are fully decoupled from the stream processors, along with ROPs operate at the core clock.

The GeForce 8800 GTS has 96 stream processors, 32 less than the 8800 GTX. These 96 stream processors operate at a slightly lower frequency of 1,200 MHz. The GTS version also has a slightly lower core clock of 500 MHz, losing 75 MHz in the change from GTX to GTS.

The GeForce 8800 GTX uses 768 MB of GDDR3 memory, currently the memory type that is most widely used in the graphics industry. Although the architecture does support use of GDDR4, the new memory technology will be used on later cards. The 768 MB of memory runs at a clock frequency of 1,800 MHz. The GeForce 8800 GTS also uses GDDR3 memory. The amount of memory, however, has been slightly reduced to 640 MB. Clock frequency has also been decreased by 200 MHz to 1,600 MHz.

The 8800 GTX holds a total of 12 memory chips. Each chip has a bus width of 32bits, adding up to a 384-bit bus width. The maximum bandwidth of the GeForce 8800 GTX is 86.4 GB/s. The 8800 GTS has a 320-bit memory interface with a total bandwidth of 64 GB/s running at 1,600 MHz. In the case of the GeForce 8800 GTS, the lower bus width is a result of only 10 memory chips coming installed on the card.

The below table lists the technical characteristics of the XFX GeForce 8800 GTX/GTS XXX video cards we will be reviewing. We have placed their values side by side with the default NVIDIA reference card’s characteristics for easy comparison.

The only differences between the standard 8800 GTX and 8800 GTS compared to the “XXX” versions are the frequencies they run at. The XFX GeForce 8800 GTX XXX has a core clock of 630 MHz, which is 55 MHz faster than the default NVIDIA values. Memory for the overclocked GTX is also 200 MHz faster, coming in at a total of 2,000 MHz. The XFX GeForce 8800 GTS XXX core has been overclocked a total of 10% to 500 MHz. The 640 MB of GDDR3 memory has also been factory overclocked by XFX 200 MHz to 1,8000 MHz.