Compare any two graphics cards:
Radeon HD 3870 X2 512MB vs Radeon HD 4830 512MB
IntroThe Radeon HD 3870 X2 512MB has a GPU core clock speed of 825 MHz, and the 512 MB of GDDR3 RAM runs at 900 MHz through a 256-bit bus. It also is made up of 320(64x5) SPUs, 16 TAUs, and 16 ROPs.
Compare those specifications to the Radeon HD 4830 512MB, which features core clock speeds of 575 MHz on the GPU, and 900 MHz on the 512 MB of GDDR3 RAM. It features 640(128x5) SPUs as well as 32 Texture Address Units and 16 Rasterization Operator Units.
Power Usage and Theoretical Benchmarks
Theoretically speaking, the Radeon HD 3870 X2 512MB should be quite a bit faster than the Radeon HD 4830 512MB overall. (explain)
Texel RateThe Radeon HD 3870 X2 512MB should be a lot (about 43%) more effective at AF than the Radeon HD 4830 512MB. (explain)
Pixel RateThe Radeon HD 3870 X2 512MB is quite a bit (about 187%) better at FSAA than the Radeon HD 4830 512MB, and will be capable of handling higher screen resolutions more effectively. (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 maximum amount of information (in units of megabytes per second) that can be moved past the external memory interface in a second. It's worked out by multiplying the card's bus width by the speed of its memory. In the case of DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, 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 number of texture map elements (texels) that are processed in one second. This number is calculated by multiplying the total amount of texture units by the core clock speed of the chip. The higher the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.
Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly write to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.