Radeon HD 4870 X2 vs Radeon HD 5870

Intro

Compare those specifications to the Radeon HD 5870, which comes with GPU clock speed of 850 MHz, and 1024 MB of GDDR5 memory set to run at 1200 MHz through a 256-bit bus. It also is comprised of 1600(320x5) SPUs, 80 Texture Address Units, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 5870		188 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 162 Watts (86%)

Memory Bandwidth

Performance-wise, the Radeon HD 4870 X2 should in theory be quite a bit superior to the Radeon HD 5870 overall. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 5870		153600 MB/sec
	Difference: 76800 (50%)

Texel Rate

The Radeon HD 5870 is a small bit (approximately 13%) faster with regards to AF than the Radeon HD 4870 X2. (explain)

Radeon HD 5870		68000 Mtexels/sec
Radeon HD 4870 X2		60000 Mtexels/sec
	Difference: 8000 (13%)

Pixel Rate

The Radeon HD 5870 is a small bit (about 13%) faster with regards to FSAA than the Radeon HD 4870 X2, and also able to handle higher resolutions without losing too much performance. (explain)

Radeon HD 5870		27200 Mpixels/sec
Radeon HD 4870 X2		24000 Mpixels/sec
	Difference: 3200 (13%)

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 data (measured in megabytes per second) that can be moved over the external memory interface in one second. It is calculated by multiplying the card's bus width by the speed of its memory. If it uses DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, the faster the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be processed in one second. This is calculated by multiplying the total texture units by the core clock speed of the chip. The better the texel rate, the better the video 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 number of pixels the video card could possibly write to its local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the number of colour ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.