Radeon HD 3870 X2 512MB vs Radeon HD 6990

Intro

Compare those specs to the Radeon HD 6990, which comes with a clock frequency of 830 MHz and a GDDR5 memory speed of 1250 MHz. It also features a 256-bit memory bus, and uses a 40 nm design. It features 1536 SPUs, 96 Texture Address Units, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically, the Radeon HD 6990 should perform much faster than the Radeon HD 3870 X2 512MB in general. (explain)

Radeon HD 6990		320000 MB/sec
Radeon HD 3870 X2 512MB		115200 MB/sec
	Difference: 204800 (178%)

Texel Rate

The Radeon HD 6990 is a lot (about 504%) faster with regards to texture filtering than the Radeon HD 3870 X2 512MB. (explain)

Radeon HD 6990		159360 Mtexels/sec
Radeon HD 3870 X2 512MB		26400 Mtexels/sec
	Difference: 132960 (504%)

Pixel Rate

The Radeon HD 6990 is quite a bit (more or less 101%) better at FSAA than the Radeon HD 3870 X2 512MB, and will be capable of handling higher screen resolutions more effectively. (explain)

Radeon HD 6990		53120 Mpixels/sec
Radeon HD 3870 X2 512MB		26400 Mpixels/sec
	Difference: 26720 (101%)

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 largest amount of information (counted in MB per second) that can be transported past the external memory interface in a second. It's calculated by multiplying the bus width by the speed of its memory. In the case of DDR type RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels the video card can possibly record to its local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.