Radeon HD 4870 X2 vs Radeon HD 7870

Intro

Compare that to the Radeon HD 7870, which comes with a GPU core clock speed of 1000 MHz, and 2048 MB of GDDR5 memory set to run at 1200 MHz through a 256-bit bus. It also features 1280 SPUs, 80 TAUs, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7870		175 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 175 Watts (100%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 X2 should be quite a bit faster than the Radeon HD 7870 in general. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 7870		153600 MB/sec
	Difference: 76800 (50%)

Texel Rate

The Radeon HD 7870 will be much (approximately 33%) more effective at AF than the Radeon HD 4870 X2. (explain)

Radeon HD 7870		80000 Mtexels/sec
Radeon HD 4870 X2		60000 Mtexels/sec
	Difference: 20000 (33%)

Pixel Rate

If using high levels of AA is important to you, then the Radeon HD 7870 is superior to the Radeon HD 4870 X2, by a large margin. (explain)

Radeon HD 7870		32000 Mpixels/sec
Radeon HD 4870 X2		24000 Mpixels/sec
	Difference: 8000 (33%)

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 information (measured in MB per second) that can be transported across the external memory interface within a second. The number is calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR type RAM, it should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied in one second. This figure is calculated by multiplying the total texture units of the card by the core speed of the chip. The better the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum number of pixels the video card could possibly record to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.