Radeon HD 3870 X2 1GB vs Radeon HD 4890 2GB

Intro

Compare those specifications to the Radeon HD 4890 2GB, which makes use of a 55 nm design. AMD has clocked the core frequency at 1000 MHz. The GDDR5 memory works at a speed of 975 MHz on this model. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

As far as performance goes, the Radeon HD 3870 X2 1GB should theoretically be a small bit superior to the Radeon HD 4890 2GB in general. (explain)

Radeon HD 3870 X2 1GB		144128 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 19328 (15%)

Texel Rate

The Radeon HD 4890 2GB is a lot (about 52%) more effective at texture filtering than the Radeon HD 3870 X2 1GB. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 3870 X2 1GB		26400 Mtexels/sec
	Difference: 13600 (52%)

Pixel Rate

The Radeon HD 3870 X2 1GB will be quite a bit (about 65%) faster with regards to FSAA than the Radeon HD 4890 2GB, and able to handle higher resolutions without losing too much performance. (explain)

Radeon HD 3870 X2 1GB		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 data (measured in MB per second) that can be moved over the external memory interface in one second. The number is calculated by multiplying the card's interface width by the speed of its memory. If the card has DDR RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, 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 texture map elements (texels) that are processed in one second. This figure is calculated by multiplying the total amount of texture units by the core clock speed of the chip. The higher this number, the better the graphics 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 number of pixels the graphics card could possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Render Output Units by the the core 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 fill rate also depends on many 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.