Radeon HD 3870 X2 512MB vs Radeon HD 6790

Intro

Compare all of that to the Radeon HD 6790, which comes with a core clock speed of 840 MHz and a GDDR5 memory frequency of 1050 MHz. It also uses a 256-bit bus, and uses a 40 nm design. It is made up of 800 SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 6790 should be 17% quicker than the Radeon HD 3870 X2 512MB in general, because of its greater data rate. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 3870 X2 512MB		115200 MB/sec
	Difference: 19200 (17%)

Texel Rate

The Radeon HD 6790 is much (approximately 27%) faster with regards to AF than the Radeon HD 3870 X2 512MB. (explain)

Radeon HD 6790		33600 Mtexels/sec
Radeon HD 3870 X2 512MB		26400 Mtexels/sec
	Difference: 7200 (27%)

Pixel Rate

If running with high levels of AA is important to you, then the Radeon HD 3870 X2 512MB is superior to the Radeon HD 6790, by a large margin. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 6790		13440 Mpixels/sec
	Difference: 12960 (96%)

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 maximum amount of data (in units of MB per second) that can be transferred over the external memory interface within a second. It is calculated by multiplying the card's bus width by its memory speed. If it uses DDR RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster 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 applied per second. This number is worked out by multiplying the total amount of texture units of the card by the core clock speed of the chip. The higher this number, the better the graphics 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 that the graphics chip could possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate also depends on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.