Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 260
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 SPUs, 32 Texture Address Units, and 16 Raster Operation Units.
Compare that to the GeForce GTX 260, which has GPU clock speed of 576 MHz, and 896 MB of GDDR3 memory set to run at 999 MHz through a 448-bit bus. It also is comprised of 192 Stream Processors, 64 Texture Address Units, and 28 ROPs.
(No game benchmarks for this combination yet.)
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The GeForce GTX 260 should theoretically be much faster than the GeForce GT 640 DDR3 in general. (explain)
Texel RateThe GeForce GTX 260 is a lot (about 28%) faster with regards to anisotropic filtering than the GeForce GT 640 DDR3. (explain)
Pixel RateIf using a high screen resolution is important to you, then the GeForce GTX 260 is a better choice, but only just. (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 transported over the external memory interface in one second. It is worked out by multiplying the card's bus width by its memory clock speed. If it uses DDR RAM, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better 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 applied in one second. This number is worked out by multiplying the total number of texture units by the core speed of the chip. The better the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.
Pixel Rate: Pixel rate is the most pixels that the graphics card can possibly record to the local memory per second - measured in millions of pixels per second. The number is worked out by multiplying the number of Render Output Units by the clock 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 bandwidth is, the lower the ability to get to the maximum fill rate.