Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 260
IntroThe GeForce GT 640 DDR3 comes with a GPU clock 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 features 384 SPUs, 32 Texture Address Units, and 16 ROPs.
Compare those specifications to the GeForce GTX 260, which has a core clock frequency of 576 MHz and a GDDR3 memory frequency of 999 MHz. It also makes use of a 448-bit memory bus, and makes use of a 65 nm design. It is made up of 192 SPUs, 64 Texture Address Units, and 28 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Theoretically speaking, the GeForce GTX 260 should be a lot faster than the GeForce GT 640 DDR3 in general. (explain)
Texel RateThe GeForce GTX 260 is quite a bit (approximately 28%) faster with regards to texture filtering than the GeForce GT 640 DDR3. (explain)
Pixel RateThe GeForce GTX 260 will be just a bit (more or less 12%) more effective at full screen anti-aliasing than the GeForce GT 640 DDR3, and should be capable of handling higher 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 maximum amount of data (counted in MB per second) that can be moved across the external memory interface in a second. It is worked out by multiplying the bus width by its memory speed. If the card has DDR type memory, it must be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, 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 amount of texture map elements (texels) that are processed in one second. This figure is calculated by multiplying the total number of texture units of the card by the core clock 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 in one second.
Pixel Rate: Pixel rate is the maximum number of pixels the video 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 ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.