GeForce 8800 GTS (G80) 640MB vs Radeon HD 3870 X2 1GB

Intro

Compare all that to the Radeon HD 3870 X2 1GB, which comes with a core clock frequency of 825 MHz and a GDDR4 memory frequency of 1126 MHz. It also uses a 256-bit memory bus, and makes use of a 55 nm design. It is comprised of 320(64x5) SPUs, 16 Texture Address Units, and 16 ROPs.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically speaking, the Radeon HD 3870 X2 1GB is 127% faster than the GeForce 8800 GTS (G80) 640MB overall, because of its higher data rate. (explain)

Radeon HD 3870 X2 1GB		144128 MB/sec
GeForce 8800 GTS (G80) 640MB		63360 MB/sec
	Difference: 80768 (127%)

Texel Rate

The Radeon HD 3870 X2 1GB will be just a bit (about 7%) better at AF than the GeForce 8800 GTS (G80) 640MB. (explain)

Radeon HD 3870 X2 1GB		26400 Mtexels/sec
GeForce 8800 GTS (G80) 640MB		24624 Mtexels/sec
	Difference: 1776 (7%)

Pixel Rate

The Radeon HD 3870 X2 1GB is a lot (about 157%) faster with regards to full screen anti-aliasing than the GeForce 8800 GTS (G80) 640MB, and also will be able to handle higher resolutions better. (explain)

Radeon HD 3870 X2 1GB		26400 Mpixels/sec
GeForce 8800 GTS (G80) 640MB		10260 Mpixels/sec
	Difference: 16140 (157%)

Please note that the above 'benchmarks' are all just theoretical - the results were calculated based on the card's specifications, and real-world performance may (and probably will) vary at least a bit.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the max amount of data (in units of MB per second) that can be transported across the external memory interface in a second. It's worked out by multiplying the card's interface width by its memory speed. If it uses DDR type memory, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied in one second. This is worked out by multiplying the total amount of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip can possibly write to its local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the number of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.