Compare any two graphics cards:
GeForce GTS 250 1GB vs Radeon HD 3870 X2 512MB
IntroThe GeForce GTS 250 1GB comes with a GPU core clock speed of 738 MHz, and the 1024 MB of GDDR3 memory runs at 1100 MHz through a 256-bit bus. It also features 128 SPUs, 64 Texture Address Units, and 16 Raster Operation Units.
Compare those specifications to the Radeon HD 3870 X2 512MB, which has a GPU core clock speed of 825 MHz, and 512 MB of GDDR3 RAM running at 900 MHz through a 256-bit bus. It also is comprised of 320(64x5) SPUs, 16 Texture Address Units, and 16 ROPs.
Power Usage and Theoretical Benchmarks
As far as performance goes, the Radeon HD 3870 X2 512MB should theoretically be much superior to the GeForce GTS 250 1GB overall. (explain)
Texel RateThe GeForce GTS 250 1GB is much (more or less 79%) faster with regards to texture filtering than the Radeon HD 3870 X2 512MB. (explain)
Pixel RateThe Radeon HD 3870 X2 512MB will be much (about 124%) better at full screen anti-aliasing than the GeForce GTS 250 1GB, and also should be able to handle higher screen resolutions without slowing down too much. (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 (in units of MB per second) that can be transported past the external memory interface within a second. It is calculated by multiplying the bus width by its memory speed. If the card has DDR memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.
Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are applied in one second. This number is calculated by multiplying the total texture units by the core speed of the chip. The better 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 one second.
Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly write to the local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the number of 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 output rate is also dependant on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.