Radeon HD 4870 X2 vs Radeon HD 6870

Intro

Compare that to the Radeon HD 6870, which makes use of a 40 nm design. AMD has set the core frequency at 900 MHz. The GDDR5 memory runs at a speed of 1050 MHz on this particular card. It features 1120 SPUs along with 56 TAUs and 32 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6870		151 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 199 Watts (132%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 X2 is 71% faster than the Radeon HD 6870 overall, due to its higher data rate. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 6870		134400 MB/sec
	Difference: 96000 (71%)

Texel Rate

The Radeon HD 4870 X2 is just a bit (more or less 19%) better at texture filtering than the Radeon HD 6870. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 6870		50400 Mtexels/sec
	Difference: 9600 (19%)

Pixel Rate

The Radeon HD 6870 is a little bit (approximately 20%) more effective at full screen anti-aliasing than the Radeon HD 4870 X2, and also should be able to handle higher screen resolutions without losing too much performance. (explain)

Radeon HD 6870		28800 Mpixels/sec
Radeon HD 4870 X2		24000 Mpixels/sec
	Difference: 4800 (20%)

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 (in units of megabytes per second) that can be moved over the external memory interface in a second. The number is calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied per second. This number is calculated by multiplying the total amount of texture units by the core speed of the chip. The better the texel rate, 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 number of pixels 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 ROPs by the the core 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 also depends on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.