Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 580 3GB
IntroThe GeForce GT 640 DDR3 comes with a core clock speed of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also uses a 128-bit bus, and uses a 28 nm design. It features 384 SPUs, 32 TAUs, and 16 Raster Operation Units.
Compare that to the GeForce GTX 580 3GB, which has GPU core speed of 772 MHz, and 3072 MB of GDDR5 RAM set to run at 1002 MHz through a 384-bit bus. It also features 512 SPUs, 64 Texture Address Units, and 48 Raster Operation Units.
(No game benchmarks for this combination yet.)
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
In theory, the GeForce GTX 580 3GB is 237% quicker than the GeForce GT 640 DDR3 overall, because of its higher bandwidth. (explain)
Texel RateThe GeForce GTX 580 3GB is much (more or less 72%) more effective at AF than the GeForce GT 640 DDR3. (explain)
Pixel RateIf running with a high screen resolution is important to you, then the GeForce GTX 580 3GB is a better choice, and very much so. (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 maximum amount of data (counted in megabytes per second) that can be transferred past the external memory interface within a second. It's worked out by multiplying the interface width by the speed of its memory. In the case of DDR memory, it should be multiplied by 2 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 higher screen resolutions.
Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This is worked out by multiplying the total texture units by the core speed of the chip. The higher the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.
Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly record to the local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the amount of Raster Operations Pipelines by the the core clock speed. ROPs (Raster Operations Pipelines - aka 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 bandwidth is, the lower the potential to get to the max fill rate.