Radeon HD 4870 512MB vs Radeon HD 4870 X2

Intro

Compare all that to the Radeon HD 4870 X2, which features GPU clock speed of 750 MHz, and 1024 MB of GDDR5 memory set to run at 900 MHz through a 256-bit bus. It also is made up of 800(160x5) Stream Processors, 40 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 512MB		150 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 200 Watts (133%)

Memory Bandwidth

The Radeon HD 4870 X2, in theory, should perform much faster than the Radeon HD 4870 512MB overall. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 4870 512MB		115200 MB/sec
	Difference: 115200 (100%)

Texel Rate

The Radeon HD 4870 X2 should be a lot (more or less 100%) better at AF than the Radeon HD 4870 512MB. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 4870 512MB		30000 Mtexels/sec
	Difference: 30000 (100%)

Pixel Rate

If using high levels of AA is important to you, then the Radeon HD 4870 X2 is superior to the Radeon HD 4870 512MB, by a large margin. (explain)

Radeon HD 4870 X2		24000 Mpixels/sec
Radeon HD 4870 512MB		12000 Mpixels/sec
	Difference: 12000 (100%)

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 maximum amount of data (in units of MB per second) that can be transported across the external memory interface in one second. The number is calculated by multiplying the card's bus width by its memory clock speed. In the case of DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better 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 are applied per second. This figure is calculated by multiplying the total texture units of the card by the core clock speed of the chip. The better this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate 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 filling the screen with pixels (the image). The actual pixel output rate is also dependant on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.