Radeon HD 4870 X2 vs Radeon HD 7870

Intro

Compare those specifications to the Radeon HD 7870, which makes use of a 28 nm design. AMD has clocked the core speed at 1000 MHz. The GDDR5 memory is set to run at a frequency of 1200 MHz on this particular model. It features 1280 SPUs along with 80 TAUs and 32 Rasterization Operator Units.

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

The Radeon HD 4870 X2 should theoretically perform much faster than the Radeon HD 7870 overall. (explain)

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

Texel Rate

The Radeon HD 7870 should be much (more or less 33%) faster with regards to 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 running with lots of anti-aliasing is important to you, then the Radeon HD 7870 is the winner, and very much so. (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 (counted in MB per second) that can be transferred across the external memory interface in one second. The number is worked out by multiplying the interface width by its memory clock speed. If it uses DDR type memory, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied per second. This number is worked out by multiplying the total amount of texture units by the core clock speed of the chip. The better this number, the better the graphics card will be at 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 video card can 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 card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.