Radeon HD 3850 256MB vs Radeon HD 3870 X2 512MB

Intro

Compare those specifications to the Radeon HD 3870 X2 512MB, which features a GPU core clock speed of 825 MHz, and 512 MB of GDDR3 RAM set to run at 900 MHz through a 256-bit bus. It also features 320(64x5) SPUs, 16 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 3870 X2 512MB should be 117% faster than the Radeon HD 3850 256MB in general, because of its higher data rate. (explain)

Radeon HD 3870 X2 512MB		115200 MB/sec
Radeon HD 3850 256MB		52992 MB/sec
	Difference: 62208 (117%)

Texel Rate

The Radeon HD 3870 X2 512MB should be quite a bit (approximately 147%) more effective at AF than the Radeon HD 3850 256MB. (explain)

Radeon HD 3870 X2 512MB		26400 Mtexels/sec
Radeon HD 3850 256MB		10688 Mtexels/sec
	Difference: 15712 (147%)

Pixel Rate

The Radeon HD 3870 X2 512MB will be quite a bit (about 147%) more effective at AA than the Radeon HD 3850 256MB, and will be able to handle higher resolutions better. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 3850 256MB		10688 Mpixels/sec
	Difference: 15712 (147%)

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 megabytes per second) that can be moved over the external memory interface in a second. The number is calculated by multiplying the interface width by its memory speed. If the card has DDR type RAM, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly write to its local memory in a second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.