XFX 6800GS SLI Video Card Review :: 6800GS Features

11-29-2005 · Category: Hardware - Video Cards

By Benjamin Sun
  • NV42 chip
  • 0.11 micron process
  • 220 million transistors
  • Shader Model 3.0
  • Pixel Shader 3.0
  • Vertex Shader 3.0
  • HDR
  • SLI
  • OpenGL 2.0
  • Intellisample 3.0
  • Purevideo Decoder

Every video card made by NVIDIA today is Shader Model 3.0 compliant. NVIDIA first launched the GeForce 6800 series in April of 2004, a year and a half ago at a launch in San Francisco. Their competition in the form of ATI Technologies is just now launching their Shader Model 3.0 parts the X1K series. The key features for Shader Model 3.0 are support for Pixel Shader 3.0 and Vertex Shader 3.0.

Pixel Shader 3.0 differentiates itself from 2.0 in several key ways. PS 3.0 supports nearly unlimited Shader program lengths. The 6800 series can do Shader programs with up to 65,536 instructions compared to PS2.0 which supported 96 instructions in a single pass. Also important to PS3.0 is dynamic branching and looping, and an instruction set similar to Vertex Shader 3.0.

Vertex Shader 3.0 features includes nearly unlimited shader lengths, render to texture, dynamic branching and looping and a back face register. Maximum static Shader lengths in VS 2.0 is 256 instructions in a single pass, with more available through looping and branching. VS 3.0 has support for more, the 6800GS is capable of 1024 instructions in a pass, with up to 65,536 through looping and branching.

NVIDIA reintroduced the idea of using two video cards to improve 3D performance on a single motherboard for the high-end gamer with the introduction of SLI late last year. SLI stands for Scalable Link Interface. Take any two like NVIDIA based cards, for example two 6800GSs, a SLI motherboard and you have the ability to get nearly double the performance of a single card in some situations.

There are three modes of SLI: AFR, SFR and Compatibility mode. AFR stands for Alternate Frame Rendering. In AFR, each card renders a frame one after the other. This is most effective when frames are similar in information, as each card can render the scene about the same speed. SFR stands for Single Frame Rendering. In this mode each card renders part of the frame. Sometimes in a frame one video card will take up the rendering duties of most of the screen as not all parts of a screen are equal.

XFX 6800GS SLI Video Card Review SLI Bridge

SLI Bridge

XFX 6800GS SLI Video Card Review Side box shots

Side box shots

XFX 6800GS SLI Video Card Review SLI Enabled

SLI Enabled

XFX 6800GS SLI Video Card Review SLI AA


NVIDIA has introduced something called SLI AA for the cards capable of SLI. Normal AA modes are no AA, 2x AA, 4x AA (all of which are rotated grid multisample), 6X, 8XS. With NVIDIA's SLI AA 16x mode is available. What 16x mode is is each card rendering in 8XS mode. One thing to note about running 6800GS in SLI mode is that 16x mode is insanely slow.

XFX has clocked the 6800GS at a clock of 485MHz, a 60MHz overclock over the standard NVIDIA clock of 425MHz. The 6800GS has 12 pixel pipelines, giving it a fillrate of 5.85 Gigapixels a second. By way of comparison, the highest end card of 2003, the 9800XT has a fillrate of 4 Gigapixels a second.