Radeon HD 4870 X2 vs Radeon HD 6870

Intro

Compare that to the Radeon HD 6870, which features a core clock speed of 900 MHz and a GDDR5 memory speed of 1050 MHz. It also uses a 256-bit memory bus, and makes use of a 40 nm design. It is comprised of 1120 SPUs, 56 TAUs, and 32 Raster Operation 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 should be 71% quicker than the Radeon HD 6870 in general, due to its higher bandwidth. (explain)

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

Texel Rate

The Radeon HD 4870 X2 should be a little bit (about 19%) faster with regards to AF than the Radeon HD 6870. (explain)

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

Pixel Rate

If running with a high resolution is important to you, then the Radeon HD 6870 is the winner, but only just. (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: Bandwidth is the largest amount of data (in units of megabytes per second) that can be transferred over the external memory interface in a second. The number is worked out by multiplying the card's interface width by its memory clock speed. If the card has DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the card's memory bandwidth, 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 number of texture map elements (texels) that are processed in one second. This number is worked out 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 graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the most pixels that the graphics chip could possibly write to its local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the number of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the max fill rate.