Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 580 3GB
IntroThe GeForce GT 640 DDR3 features a core clock frequency of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also uses a 128-bit memory bus, and makes use of a 28 nm design. It is made up of 384 SPUs, 32 TAUs, and 16 Raster Operation Units.
Compare that to the GeForce GTX 580 3GB, which has a core clock speed of 772 MHz and a GDDR5 memory frequency of 1002 MHz. It also makes use of a 384-bit memory bus, and uses a 40 nm design. It features 512 SPUs, 64 Texture Address Units, and 48 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Performance-wise, the GeForce GTX 580 3GB should theoretically be a lot better than the GeForce GT 640 DDR3 overall. (explain)
Texel RateThe GeForce GTX 580 3GB is quite a bit (more or less 72%) better at anisotropic filtering than the GeForce GT 640 DDR3. (explain)
Pixel RateIf running with a high screen resolution is important to you, then the GeForce GTX 580 3GB is the winner, 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.
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 information (measured in MB per second) that can be transferred over the external memory interface in one second. It is worked out by multiplying the bus width by the speed of its memory. If it uses DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.
Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed per second. This number is worked out by multiplying the total amount of texture units by the core clock speed of the chip. The better this number, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.
Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly record to its local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.