Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 660 Ti
IntroThe GeForce GT 640 DDR3 has a GPU core speed of 900 MHz, and the 2048 MB of DDR3 memory is set to run at 1782 MHz through a 128-bit bus. It also is comprised of 384 Stream Processors, 32 TAUs, and 16 Raster Operation Units.
Compare those specs to the GeForce GTX 660 Ti, which has clock speeds of 915 MHz on the GPU, and 1500 MHz on the 2048 MB of GDDR5 RAM. It features 1344 SPUs along with 112 Texture Address Units and 24 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
In theory, the GeForce GTX 660 Ti should be much faster than the GeForce GT 640 DDR3 in general. (explain)
Texel RateThe GeForce GTX 660 Ti should be a lot (more or less 256%) better at AF than the GeForce GT 640 DDR3. (explain)
Pixel RateIf running with a high screen resolution is important to you, then the GeForce GTX 660 Ti is superior to the GeForce GT 640 DDR3, by a large margin. (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 data (counted in MB per second) that can be moved over the external memory interface in a second. It is calculated by multiplying the card's bus width by its memory clock speed. If the card has DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, 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 number is calculated by multiplying the total number of texture units by the core speed of the chip. The better the texel rate, 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 most pixels the graphics card can possibly record to the local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of colour ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also called 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 of the card - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.