Compare any two graphics cards:
GeForce GTX 580 3GB vs Radeon HD 6990
IntroThe GeForce GTX 580 3GB has core speeds of 772 MHz on the GPU, and 1002 MHz on the 3072 MB of GDDR5 RAM. It features 512 SPUs along with 64 TAUs and 48 ROPs.
Compare all that to the Radeon HD 6990, which comes with a clock speed of 830 MHz and a GDDR5 memory speed of 1250 MHz. It also makes use of a 256-bit memory bus, and makes use of a 40 nm design. It features 1536 SPUs, 96 TAUs, and 32 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Theoretically speaking, the Radeon HD 6990 is 66% quicker than the GeForce GTX 580 3GB overall, due to its higher data rate. (explain)
Texel RateThe Radeon HD 6990 should be much (more or less 223%) faster with regards to AF than the GeForce GTX 580 3GB. (explain)
Pixel RateIf using lots of anti-aliasing is important to you, then the Radeon HD 6990 is superior to the GeForce GTX 580 3GB, by far. (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 maximum amount of data (counted in megabytes per second) that can be moved over the external memory interface in one second. It is calculated by multiplying the card's bus width by the speed of its memory. If it uses DDR RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and higher screen 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 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 processed per second.
Pixel Rate: Pixel rate is the most pixels the graphics card can possibly record to the local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the number of ROPs by the clock speed of the card. 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 also depends on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.