Radeon HD 3870 X2 512MB vs Radeon HD 4890 2GB

Intro

Compare all that to the Radeon HD 4890 2GB, which makes use of a 55 nm design. AMD has clocked the core speed at 1000 MHz. The GDDR5 RAM works at a speed 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 4890 2GB should perform a little bit faster than the Radeon HD 3870 X2 512MB overall. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 3870 X2 512MB		115200 MB/sec
	Difference: 9600 (8%)

Texel Rate

The Radeon HD 4890 2GB will be a lot (more or less 52%) better at texture filtering than the Radeon HD 3870 X2 512MB. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 3870 X2 512MB		26400 Mtexels/sec
	Difference: 13600 (52%)

Pixel Rate

The Radeon HD 3870 X2 512MB should be a lot (approximately 65%) better at AA than the Radeon HD 4890 2GB, and also will be capable of handling higher resolutions without losing too much performance. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 4890 2GB		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: Memory bandwidth is the max amount of information (in units of MB per second) that can be transferred past the external memory interface in a second. It is worked out by multiplying the interface width by its memory speed. If it uses DDR type 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, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied in one second. This number is worked out by multiplying the total texture units by the core speed of the chip. The better the texel rate, the better the video card will be at handling 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 chip could possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.