Radeon HD 3870 X2 512MB vs Radeon HD 4850 512MB

Intro

Compare those specifications to the Radeon HD 4850 512MB, which comes with core clock speeds of 625 MHz on the GPU, and 993 MHz on the 512 MB of GDDR3 RAM. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically speaking, the Radeon HD 3870 X2 512MB should be much faster than the Radeon HD 4850 512MB in general. (explain)

Radeon HD 3870 X2 512MB		115200 MB/sec
Radeon HD 4850 512MB		63552 MB/sec
	Difference: 51648 (81%)

Texel Rate

The Radeon HD 3870 X2 512MB will be a small bit (approximately 6%) better at texture filtering than the Radeon HD 4850 512MB. (explain)

Radeon HD 3870 X2 512MB		26400 Mtexels/sec
Radeon HD 4850 512MB		25000 Mtexels/sec
	Difference: 1400 (6%)

Pixel Rate

If using a high resolution is important to you, then the Radeon HD 3870 X2 512MB is the winner, by a large margin. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 4850 512MB		10000 Mpixels/sec
	Difference: 16400 (164%)

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 data (counted in MB per second) that can be transported past the external memory interface in a second. The number is calculated by multiplying the card's interface width by its memory clock speed. If it uses DDR type memory, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, 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 number of texture map elements (texels) that are applied in one second. This figure is calculated by multiplying the total texture units by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

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