Radeon HD 3870 X2 512MB vs Radeon HD 4850 1GB

Intro

Compare that to the Radeon HD 4850 1GB, which comes with core speeds of 625 MHz on the GPU, and 993 MHz on the 1024 MB of GDDR4 memory. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 3870 X2 512MB is 81% quicker than the Radeon HD 4850 1GB in general, because of its higher data rate. (explain)

Radeon HD 3870 X2 512MB		115200 MB/sec
Radeon HD 4850 1GB		63552 MB/sec
	Difference: 51648 (81%)

Texel Rate

The Radeon HD 3870 X2 512MB will be just a bit (about 6%) better at anisotropic filtering than the Radeon HD 4850 1GB. (explain)

Radeon HD 3870 X2 512MB		26400 Mtexels/sec
Radeon HD 4850 1GB		25000 Mtexels/sec
	Difference: 1400 (6%)

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 4850 1GB, by a large margin. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 4850 1GB		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: Bandwidth is the max amount of information (in units of megabytes per second) that can be moved across the external memory interface within a second. It's worked out by multiplying the interface width by the speed of its memory. If it uses DDR type memory, it should be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly write to its local memory per second - measured in millions of pixels per second. The figure 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 rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.