Compare any two graphics cards:
GeForce GT 640 DDR3 vs Radeon HD 4850 2GB
IntroThe GeForce GT 640 DDR3 features a core clock frequency of 900 MHz and a DDR3 memory speed of 1782 MHz. It also makes use of a 128-bit bus, and makes use of a 28 nm design. It is made up of 384 SPUs, 32 TAUs, and 16 Raster Operation Units.
Compare those specifications to the Radeon HD 4850 2GB, which features a core clock frequency of 625 MHz and a GDDR4 memory speed of 993 MHz. It also uses a 256-bit bus, and uses a 55 nm design. It is comprised of 800(160x5) SPUs, 40 TAUs, and 16 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
In theory, the Radeon HD 4850 2GB is 11% quicker than the GeForce GT 640 DDR3 in general, because of its higher bandwidth. (explain)
Texel RateThe GeForce GT 640 DDR3 will be a bit (about 15%) faster with regards to anisotropic filtering than the Radeon HD 4850 2GB. (explain)
Pixel RateThe GeForce GT 640 DDR3 should be a lot (approximately 44%) better at full screen anti-aliasing than the Radeon HD 4850 2GB, and also capable of handling higher screen 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 max amount of data (measured in MB per second) that can be transported past the external memory interface in one second. The number is calculated by multiplying the bus width by the speed of its memory. If it uses DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.
Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This figure is calculated by multiplying the total texture units by the core clock speed of the chip. The better this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.
Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly write to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the number of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.