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