Radeon HD 4870 X2 vs Radeon HD 7850

Intro

Compare all of that to the Radeon HD 7850, which has a core clock frequency of 860 MHz and a GDDR5 memory speed of 1200 MHz. It also uses a 256-bit bus, and uses a 28 nm design. It is comprised of 1024 SPUs, 64 Texture Address Units, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7850		130 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 220 Watts (169%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 X2 should be 50% quicker than the Radeon HD 7850 overall, due to its greater data rate. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 7850		153600 MB/sec
	Difference: 76800 (50%)

Texel Rate

The Radeon HD 4870 X2 should be a little bit (more or less 9%) better at texture filtering than the Radeon HD 7850. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 7850		55040 Mtexels/sec
	Difference: 4960 (9%)

Pixel Rate

If running with high levels of AA is important to you, then the Radeon HD 7850 is superior to the Radeon HD 4870 X2, but it probably won't make a huge difference. (explain)

Radeon HD 7850		27520 Mpixels/sec
Radeon HD 4870 X2		24000 Mpixels/sec
	Difference: 3520 (15%)

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 (in units of MB per second) that can be moved past the external memory interface in a second. The number is calculated by multiplying the card's bus width by its memory speed. If the card has DDR type RAM, it should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied in one second. This is worked out by multiplying the total amount of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card could possibly write to its local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.