Radeon HD 3870 X2 1GB vs Radeon HD 6990

Intro

Compare those specifications to the Radeon HD 6990, which features a GPU core clock speed of 830 MHz, and 2048 MB of GDDR5 RAM set to run at 1250 MHz through a 256-bit bus. It also features 1536 SPUs, 96 TAUs, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically speaking, the Radeon HD 6990 should perform much faster than the Radeon HD 3870 X2 1GB in general. (explain)

Radeon HD 6990		320000 MB/sec
Radeon HD 3870 X2 1GB		144128 MB/sec
	Difference: 175872 (122%)

Texel Rate

The Radeon HD 6990 should be much (about 504%) more effective at texture filtering than the Radeon HD 3870 X2 1GB. (explain)

Radeon HD 6990		159360 Mtexels/sec
Radeon HD 3870 X2 1GB		26400 Mtexels/sec
	Difference: 132960 (504%)

Pixel Rate

The Radeon HD 6990 will be a lot (about 101%) faster with regards to FSAA than the Radeon HD 3870 X2 1GB, and will be able to handle higher screen resolutions without slowing down too much. (explain)

Radeon HD 6990		53120 Mpixels/sec
Radeon HD 3870 X2 1GB		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: Memory bandwidth is the largest amount of information (measured in megabytes per second) that can be moved over the external memory interface in one second. It is worked out by multiplying the interface width by the speed of its memory. In the case of DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better 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 amount of texture map elements (texels) that are applied per second. This number is worked out by multiplying the total texture units of the card by the core clock speed of the chip. The better this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

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