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Compare any two graphics cards:
Radeon HD 3870 X2 512MB vs Radeon HD 4770
IntroThe Radeon HD 3870 X2 512MB comes with core speeds of 825 MHz on the GPU, and 900 MHz on the 512 MB of GDDR3 memory. It features 320(64x5) SPUs along with 16 TAUs and 16 Rasterization Operator Units.
Compare those specifications to the Radeon HD 4770, which has a GPU core clock speed of 750 MHz, and 512 MB of GDDR5 RAM set to run at 800 MHz through a 128-bit bus. It also is made up of 640(128x5) SPUs, 32 Texture Address Units, and 16 ROPs.
Power Usage and Theoretical Benchmarks
In theory, the Radeon HD 3870 X2 512MB should be quite a bit faster than the Radeon HD 4770 overall. (explain)
Texel RateThe Radeon HD 3870 X2 512MB is a bit (more or less 10%) more effective at anisotropic filtering than the Radeon HD 4770. (explain)
Pixel RateThe Radeon HD 3870 X2 512MB is a lot (more or less 120%) better at anti-aliasing than the Radeon HD 4770, and also will be capable of handling higher screen resolutions while still performing well. (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: Bandwidth is the max amount of information (counted in megabytes per second) that can be transferred past the external memory interface in a second. It's calculated by multiplying the bus width by its memory speed. In the case of DDR type RAM, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.
Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied per second. This number 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 graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels per second.
Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.