Radeon HD 4870 X2 vs Radeon HD 4890 2GB

Intro

Compare all that to the Radeon HD 4890 2GB, which features a core clock speed of 1000 MHz and a GDDR5 memory speed of 975 MHz. It also uses a 256-bit memory bus, and makes use of a 55 nm design. It is made up of 800(160x5) SPUs, 40 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4890 2GB		190 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 160 Watts (84%)

Memory Bandwidth

Performance-wise, the Radeon HD 4870 X2 should in theory be a lot better than the Radeon HD 4890 2GB in general. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 105600 (85%)

Texel Rate

The Radeon HD 4870 X2 is much (about 50%) faster with regards to texture filtering than the Radeon HD 4890 2GB. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 4890 2GB		40000 Mtexels/sec
	Difference: 20000 (50%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the Radeon HD 4870 X2 is the winner, and very much so. (explain)

Radeon HD 4870 X2		24000 Mpixels/sec
Radeon HD 4890 2GB		16000 Mpixels/sec
	Difference: 8000 (50%)

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 max amount of information (in units of MB per second) that can be transported over the external memory interface in a second. It's worked out by multiplying the interface width by its memory speed. If it uses DDR RAM, it must be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be processed per second. This figure is calculated 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 per 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 colour ROPs by the the card's 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 rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.