Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 260
IntroThe GeForce GT 640 DDR3 comes with core speeds of 900 MHz on the GPU, and 1782 MHz on the 2048 MB of DDR3 memory. It features 384 SPUs as well as 32 TAUs and 16 Rasterization Operator Units.
Compare those specifications to the GeForce GTX 260, which features GPU clock speed of 576 MHz, and 896 MB of GDDR3 memory running at 999 MHz through a 448-bit bus. It also features 192 Stream Processors, 64 Texture Address Units, and 28 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The GeForce GTX 260 should theoretically perform much faster than the GeForce GT 640 DDR3 overall. (explain)
Texel RateThe GeForce GTX 260 should be quite a bit (about 28%) more effective at anisotropic filtering than the GeForce GT 640 DDR3. (explain)
Pixel RateIf running with a high screen resolution is important to you, then the GeForce GTX 260 is superior to the GeForce GT 640 DDR3, though only just barely. (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 (measured in MB per second) that can be transferred past the external memory interface in one second. It's worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.
Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be processed in one second. This is worked out by multiplying the total number of 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 per second.
Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly write to its local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the amount of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the max fill rate.