Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 580 3GB
IntroThe GeForce GT 640 DDR3 uses a 28 nm design. nVidia has clocked the core frequency at 900 MHz. The DDR3 RAM runs at a speed of 1782 MHz on this specific model. It features 384 SPUs as well as 32 TAUs and 16 ROPs.
Compare that to the GeForce GTX 580 3GB, which features a clock frequency of 772 MHz and a GDDR5 memory speed of 1002 MHz. It also makes use of a 384-bit bus, and uses a 40 nm design. It features 512 SPUs, 64 Texture Address Units, and 48 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Theoretically speaking, the GeForce GTX 580 3GB will be 237% faster than the GeForce GT 640 DDR3 overall, because of its higher bandwidth. (explain)
Texel RateThe GeForce GTX 580 3GB should be much (more or less 72%) better at texture filtering than the GeForce GT 640 DDR3. (explain)
Pixel RateThe GeForce GTX 580 3GB should be a lot (about 157%) more effective at AA than the GeForce GT 640 DDR3, and able to handle higher 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.
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 information (measured in MB per second) that can be transferred across the external memory interface within a second. The number is calculated by multiplying the card's interface width by its memory speed. If the card has DDR RAM, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. 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 texture map elements (texels) that are applied in one second. This is calculated by multiplying the total number of texture units of the card by the core speed of the chip. The higher the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.
Pixel Rate: Pixel rate is the most pixels the video card can possibly record to the local memory in one 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 - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.