GeForce GTX 580 3GB vs Radeon HD 3870 X2 1GB

Intro

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

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the GeForce GTX 580 3GB should be 33% quicker than the Radeon HD 3870 X2 1GB overall, due to its greater bandwidth. (explain)

GeForce GTX 580 3GB		192384 MB/sec
Radeon HD 3870 X2 1GB		144128 MB/sec
	Difference: 48256 (33%)

Texel Rate

The GeForce GTX 580 3GB will be quite a bit (approximately 87%) faster with regards to texture filtering than the Radeon HD 3870 X2 1GB. (explain)

GeForce GTX 580 3GB		49408 Mtexels/sec
Radeon HD 3870 X2 1GB		26400 Mtexels/sec
	Difference: 23008 (87%)

Pixel Rate

If running with high levels of AA is important to you, then the GeForce GTX 580 3GB is a better choice, by far. (explain)

GeForce GTX 580 3GB		37056 Mpixels/sec
Radeon HD 3870 X2 1GB		26400 Mpixels/sec
	Difference: 10656 (40%)

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: Memory bandwidth is the largest amount of information (in units of megabytes per second) that can be transferred over the external memory interface in one second. It's worked out by multiplying the card's bus width by its memory clock speed. If it uses DDR type memory, it must be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed per second. This is worked out by multiplying the total number of texture units by the core speed of the chip. The better this number, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly write to its local memory per second - measured in millions of pixels per second. The number is calculated by multiplying the number of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the max fill rate.