Compare any two graphics cards:
Radeon HD 4790 vs Radeon HD 4850 X2 1GB
IntroThe Radeon HD 4790 features a core clock frequency of 600 MHz and a GDDR5 memory speed of 800 MHz. It also uses a 256-bit bus, and makes use of a 55 nm design. It is made up of 640(128x5) SPUs, 32 Texture Address Units, and 16 ROPs.
Compare all that to the Radeon HD 4850 X2 1GB, which comes with GPU core speed of 625 MHz, and 1024 MB of GDDR3 memory running at 993 MHz through a 256-bit bus. It also is comprised of 800(160x5) Stream Processors, 40 Texture Address Units, and 16 ROPs.
Power Usage and Theoretical Benchmarks
Performance-wise, the Radeon HD 4850 X2 1GB should in theory be quite a bit better than the Radeon HD 4790 in general. (explain)
Texel RateThe Radeon HD 4850 X2 1GB will be much (more or less 160%) more effective at AF than the Radeon HD 4790. (explain)
Pixel RateIf using a high screen resolution is important to you, then the Radeon HD 4850 X2 1GB is the winner, 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 largest amount of data (counted in megabytes per second) that can be transported over the external memory interface in a second. The number is calculated by multiplying the card's interface width by the speed of its memory. If the card has DDR type RAM, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the 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 in one second. This figure is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The higher the texel rate, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.
Pixel Rate: Pixel rate is the most pixels the graphics card can possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Render Output Units by the the core speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the max fill rate.