Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 660 Ti
IntroThe GeForce GT 640 DDR3 features a core clock frequency of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also makes use of a 128-bit bus, and uses a 28 nm design. It features 384 SPUs, 32 TAUs, and 16 Raster Operation Units.
Compare those specifications to the GeForce GTX 660 Ti, which has a core clock speed of 915 MHz and a GDDR5 memory frequency of 1500 MHz. It also features a 192-bit bus, and uses a 28 nm design. It is comprised of 1344 SPUs, 112 Texture Address Units, and 24 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
In theory, the GeForce GTX 660 Ti will be 153% faster than the GeForce GT 640 DDR3 overall, due to its greater data rate. (explain)
Texel RateThe GeForce GTX 660 Ti is quite a bit (approximately 256%) more effective at AF than the GeForce GT 640 DDR3. (explain)
Pixel RateThe GeForce GTX 660 Ti should be a lot (more or less 53%) faster with regards to AA than the GeForce GT 640 DDR3, and will be capable of handling higher screen resolutions without losing too much performance. (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 data (counted in MB per second) that can be moved past the external memory interface within a second. The number is worked out by multiplying the card's bus width by its memory speed. In the case of DDR type memory, it must be multiplied by 2 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 anti-aliasing, High Dynamic Range and high resolutions.
Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be applied per second. This is worked out by multiplying the total number of texture units of the card by the core speed of the chip. The higher this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.
Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. The number is calculated by multiplying the number of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes 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 reach the maximum fill rate.