Compare any two graphics cards:
GeForce GT 640 DDR3 vs Radeon HD 7990
IntroThe GeForce GT 640 DDR3 has a GPU clock speed of 900 MHz, and the 2048 MB of DDR3 RAM runs at 1782 MHz through a 128-bit bus. It also features 384 Stream Processors, 32 Texture Address Units, and 16 Raster Operation Units.
Compare those specifications to the Radeon HD 7990, which features clock speeds of 950 MHz on the GPU, and 1500 MHz on the 3072 MB of GDDR5 memory. It features 2048 SPUs along with 128 TAUs and 32 Rasterization Operator Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The Radeon HD 7990 should theoretically perform a lot faster than the GeForce GT 640 DDR3 overall. (explain)
Texel RateThe Radeon HD 7990 should be much (about 744%) better at AF than the GeForce GT 640 DDR3. (explain)
Pixel RateThe Radeon HD 7990 should be a lot (more or less 322%) better at AA than the GeForce GT 640 DDR3, and should be capable of handling higher screen resolutions better. (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 (in units of MB per second) that can be transported across the external memory interface in a second. It's worked out by multiplying the bus width by its memory clock speed. If it uses DDR type memory, it must be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and high resolutions.
Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied in one second. This figure is worked out by multiplying the total number of texture units of the card by the core speed of the chip. The better the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.
Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate is also dependant 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.