Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 580 3GB
IntroThe GeForce GT 640 DDR3 has core 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 ROPs.
Compare that to the GeForce GTX 580 3GB, which comes with a core clock speed of 772 MHz and a GDDR5 memory speed of 1002 MHz. It also uses a 384-bit memory bus, and uses a 40 nm design. It is made up of 512 SPUs, 64 TAUs, and 48 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The GeForce GTX 580 3GB should in theory perform a lot faster than the GeForce GT 640 DDR3 in general. (explain)
Texel RateThe GeForce GTX 580 3GB will be quite a bit (approximately 72%) more effective at anisotropic filtering than the GeForce GT 640 DDR3. (explain)
Pixel RateThe GeForce GTX 580 3GB is quite a bit (approximately 157%) better at anti-aliasing than the GeForce GT 640 DDR3, and also will be able to handle higher resolutions better. (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 (counted in MB per second) that can be moved over the external memory interface in a second. It is worked out by multiplying the interface width by the speed of its memory. If it uses DDR memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.
Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be applied in one second. This is calculated by multiplying the total number of texture units by the core clock 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 maximum amount of pixels the video card can possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.