Radeon HD 3870 X2 1GB vs Radeon HD 6750 1GB

Intro

Compare those specifications to the Radeon HD 6750 1GB, which comes with a clock frequency of 725 MHz and a GDDR5 memory speed of 1000 MHz. It also uses a 128-bit bus, and uses a 40 nm design. It is made up of 720 SPUs, 36 Texture Address Units, and 16 Raster Operation Units.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Memory Bandwidth

The Radeon HD 3870 X2 1GB, in theory, should be a lot faster than the Radeon HD 6750 1GB overall. (explain)

Radeon HD 3870 X2 1GB		144128 MB/sec
Radeon HD 6750 1GB		64000 MB/sec
	Difference: 80128 (125%)

Texel Rate

The Radeon HD 3870 X2 1GB is a small bit (more or less 1%) more effective at AF than the Radeon HD 6750 1GB. (explain)

Radeon HD 3870 X2 1GB		26400 Mtexels/sec
Radeon HD 6750 1GB		26100 Mtexels/sec
	Difference: 300 (1%)

Pixel Rate

If using high levels of AA is important to you, then the Radeon HD 3870 X2 1GB is superior to the Radeon HD 6750 1GB, by a large margin. (explain)

Radeon HD 3870 X2 1GB		26400 Mpixels/sec
Radeon HD 6750 1GB		11600 Mpixels/sec
	Difference: 14800 (128%)

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 information (in units of MB per second) that can be transported over the external memory interface within a second. The number is worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's 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 can be applied in one second. This is calculated by multiplying the total amount of 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 applied in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number 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 output rate is also dependant on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.