Radeon HD 4870 1GB vs Radeon HD 4870 X2

Intro

Compare those specs to the Radeon HD 4870 X2, which comes with a core clock frequency of 750 MHz and a GDDR5 memory speed of 900 MHz. It also uses a 256-bit bus, and uses a 55 nm design. It is made up of 800(160x5) SPUs, 40 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 1GB		150 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 200 Watts (133%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 X2 will be 100% faster than the Radeon HD 4870 1GB overall, because of its higher bandwidth. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 4870 1GB		115200 MB/sec
	Difference: 115200 (100%)

Texel Rate

The Radeon HD 4870 X2 should be much (more or less 100%) better at anisotropic filtering than the Radeon HD 4870 1GB. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 4870 1GB		30000 Mtexels/sec
	Difference: 30000 (100%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 4870 X2 is a better choice, by a large margin. (explain)

Radeon HD 4870 X2		24000 Mpixels/sec
Radeon HD 4870 1GB		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 (counted in megabytes per second) that can be moved past the external memory interface within a second. It is worked out by multiplying the card's bus width by its memory clock speed. In the case of DDR RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the memory bandwidth, the better 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 amount of texture map elements (texels) that can be processed per second. This figure is worked out by multiplying the total number of texture units of the card by the core 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 processed per second.

Pixel Rate: Pixel rate is the most pixels the graphics card could possibly record to its local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of ROPs 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 rate is also dependant on quite a few other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.