Compare any two graphics cards:
Radeon HD 3870 X2 1GB vs Radeon HD 5770
IntroThe Radeon HD 3870 X2 1GB comes with a clock speed of 825 MHz and a GDDR4 memory speed of 1126 MHz. It also uses a 256-bit memory bus, and uses a 55 nm design. It is comprised of 320(64x5) SPUs, 16 TAUs, and 16 Raster Operation Units.
Compare all of that to the Radeon HD 5770, which has core clock speeds of 850 MHz on the GPU, and 1200 MHz on the 1024 MB of GDDR5 RAM. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 ROPs.
Power Usage and Theoretical Benchmarks
The Radeon HD 3870 X2 1GB should theoretically be a lot faster than the Radeon HD 5770 overall. (explain)
Texel RateThe Radeon HD 5770 should be a lot (about 29%) better at AF than the Radeon HD 3870 X2 1GB. (explain)
Pixel RateIf running with high levels of AA is important to you, then the Radeon HD 3870 X2 1GB is a better choice, and very much so. (explain)
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.
Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.
Memory Bandwidth: Memory bandwidth is the max amount of data (measured in megabytes per second) that can be moved over the external memory interface within a second. It's worked out by multiplying the bus width by its memory clock speed. If it uses DDR memory, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.
Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are applied per second. This figure 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 calculated by multiplying the number of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.