Radeon HD 4850 X2 512MB vs Radeon HD 4870 2GB

Intro

Compare that to the Radeon HD 4870 2GB, which comes with core clock speeds of 750 MHz on the GPU, and 900 MHz on the 2048 MB of GDDR5 memory. 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 2GB		150 Watts
Radeon HD 4850 X2 512MB		250 Watts
	Difference: 100 Watts (67%)

Memory Bandwidth

As far as performance goes, the Radeon HD 4850 X2 512MB should in theory be a small bit superior to the Radeon HD 4870 2GB in general. (explain)

Radeon HD 4850 X2 512MB		127104 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 11904 (10%)

Texel Rate

The Radeon HD 4850 X2 512MB will be a lot (approximately 67%) better at AF than the Radeon HD 4870 2GB. (explain)

Radeon HD 4850 X2 512MB		50000 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 20000 (67%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 4850 X2 512MB is a better choice, by a large margin. (explain)

Radeon HD 4850 X2 512MB		20000 Mpixels/sec
Radeon HD 4870 2GB		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 largest amount of information (counted in MB per second) that can be moved across the external memory interface in one second. The number is worked out by multiplying the bus width by the speed of its memory. In the case of DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better 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 figure is calculated 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 card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the most pixels that the graphics chip can possibly record to the local memory per second - measured in millions of pixels per second. The number is calculated by multiplying the number of Render Output Units by the clock 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 output rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.