Radeon HD 3870 X2 1GB vs Radeon HD 4890 1GB

Intro

Compare those specs to the Radeon HD 4890 1GB, which makes use of a 55 nm design. AMD has clocked the core speed at 1000 MHz. The GDDR5 RAM works at a frequency of 975 MHz on this particular model. It features 800(160x5) SPUs as well as 40 TAUs and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 3870 X2 1GB should be 15% faster than the Radeon HD 4890 1GB overall, due to its greater data rate. (explain)

Radeon HD 3870 X2 1GB		144128 MB/sec
Radeon HD 4890 1GB		124800 MB/sec
	Difference: 19328 (15%)

Texel Rate

The Radeon HD 4890 1GB is quite a bit (more or less 52%) better at texture filtering than the Radeon HD 3870 X2 1GB. (explain)

Radeon HD 4890 1GB		40000 Mtexels/sec
Radeon HD 3870 X2 1GB		26400 Mtexels/sec
	Difference: 13600 (52%)

Pixel Rate

If running with a high resolution is important to you, then the Radeon HD 3870 X2 1GB is superior to the Radeon HD 4890 1GB, by far. (explain)

Radeon HD 3870 X2 1GB		26400 Mpixels/sec
Radeon HD 4890 1GB		16000 Mpixels/sec
	Difference: 10400 (65%)

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 max amount of data (counted in MB per second) that can be transferred over the external memory interface in one second. It's worked out by multiplying the card's bus width by its memory clock speed. If the card has DDR RAM, it should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better 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 amount of texture map elements (texels) that are processed in one second. This is calculated by multiplying the total texture units of the card by the core clock speed of the chip. The higher this number, the better the card will be at handling 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 graphics card can possibly write to its local memory in a second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the max fill rate.