Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 260
IntroThe GeForce GT 640 DDR3 comes with clock speeds of 900 MHz on the GPU, and 1782 MHz on the 2048 MB of DDR3 RAM. It features 384 SPUs as well as 32 Texture Address Units and 16 Rasterization Operator Units.
Compare those specs to the GeForce GTX 260, which features a core clock speed of 576 MHz and a GDDR3 memory frequency of 999 MHz. It also makes use of a 448-bit memory bus, and uses a 65 nm design. It is comprised of 192 SPUs, 64 TAUs, and 28 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Performance-wise, the GeForce GTX 260 should in theory be a lot superior to the GeForce GT 640 DDR3 overall. (explain)
Texel RateThe GeForce GTX 260 will be a lot (about 28%) more effective at AF than the GeForce GT 640 DDR3. (explain)
Pixel RateThe GeForce GTX 260 should be a bit (more or less 12%) more effective at anti-aliasing than the GeForce GT 640 DDR3, and able to handle higher resolutions more effectively. (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 information (in units of MB per second) that can be transferred across the external memory interface in one second. The number is calculated by multiplying the bus width by the speed of its memory. In the case of DDR type RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.
Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be processed per second. This figure is worked out by multiplying the total amount of texture units by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels per second.
Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card can possibly write to its local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the amount of Render Output Units by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.