Radeon HD 4850 X2 1GB vs Radeon HD 4870 512MB

Intro

Compare those specs to the Radeon HD 4870 512MB, which comes with core clock speeds of 750 MHz on the GPU, and 900 MHz on the 512 MB of GDDR5 RAM. It features 800(160x5) SPUs along with 40 TAUs and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 512MB		150 Watts
Radeon HD 4850 X2 1GB		250 Watts
	Difference: 100 Watts (67%)

Memory Bandwidth

In theory, the Radeon HD 4850 X2 1GB should be 10% faster than the Radeon HD 4870 512MB in general, because of its higher data rate. (explain)

Radeon HD 4850 X2 1GB		127104 MB/sec
Radeon HD 4870 512MB		115200 MB/sec
	Difference: 11904 (10%)

Texel Rate

The Radeon HD 4850 X2 1GB should be quite a bit (more or less 67%) more effective at AF than the Radeon HD 4870 512MB. (explain)

Radeon HD 4850 X2 1GB		50000 Mtexels/sec
Radeon HD 4870 512MB		30000 Mtexels/sec
	Difference: 20000 (67%)

Pixel Rate

The Radeon HD 4850 X2 1GB will be much (more or less 67%) faster with regards to AA than the Radeon HD 4870 512MB, and also able to handle higher resolutions without slowing down too much. (explain)

Radeon HD 4850 X2 1GB		20000 Mpixels/sec
Radeon HD 4870 512MB		12000 Mpixels/sec
	Difference: 8000 (67%)

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 moved past the external memory interface within a second. The number is worked out by multiplying the card's interface width by its memory speed. In the case of DDR type memory, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher 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 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 better this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels per second.

Pixel Rate: Pixel rate is the maximum amount of pixels the video card could possibly write to the local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.