Radeon HD 4870 X2 vs Radeon HD 7870 XT

Intro

Compare those specifications to the Radeon HD 7870 XT, which comes with core clock speeds of 925 MHz on the GPU, and 1500 MHz on the 2048 MB of GDDR5 memory. It features 1536 SPUs as well as 96 TAUs and 32 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7870 XT		185 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 165 Watts (89%)

Memory Bandwidth

Theoretically, the Radeon HD 4870 X2 should be a little bit faster than the Radeon HD 7870 XT overall. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 7870 XT		192000 MB/sec
	Difference: 38400 (20%)

Texel Rate

The Radeon HD 7870 XT will be much (about 48%) better at AF than the Radeon HD 4870 X2. (explain)

Radeon HD 7870 XT		88800 Mtexels/sec
Radeon HD 4870 X2		60000 Mtexels/sec
	Difference: 28800 (48%)

Pixel Rate

The Radeon HD 7870 XT is quite a bit (about 23%) better at full screen anti-aliasing than the Radeon HD 4870 X2, and should be able to handle higher resolutions while still performing well. (explain)

Radeon HD 7870 XT		29600 Mpixels/sec
Radeon HD 4870 X2		24000 Mpixels/sec
	Difference: 5600 (23%)

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 (counted in MB per second) that can be moved over the external memory interface within a second. It's worked out by multiplying the bus width by the speed of its memory. If the card has DDR RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed per second. This number is calculated by multiplying the total number of texture units by the core 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 in one second.

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