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 frequency of 1782 MHz. It also features a 128-bit bus, and makes use of a 28 nm design. It features 384 SPUs, 32 Texture Address Units, and 16 Raster Operation Units.
Compare all that to the Radeon HD 4850 2GB, which makes use of a 55 nm design. AMD has clocked the core frequency at 625 MHz. The GDDR4 memory works at a frequency of 993 MHz on this particular model. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 Rasterization Operator Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
As far as performance goes, the Radeon HD 4850 2GB should in theory be a bit superior to the GeForce GT 640 DDR3 in general. (explain)
Texel RateThe GeForce GT 640 DDR3 will be a little bit (more or less 15%) more effective at AF than the Radeon HD 4850 2GB. (explain)
Pixel RateThe GeForce GT 640 DDR3 will be much (about 44%) faster with regards to full screen anti-aliasing than the Radeon HD 4850 2GB, and will be able to handle higher resolutions without slowing down too much. (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 megabytes per second) that can be moved across the external memory interface in a second. It's calculated by multiplying the card's bus width by its memory speed. If it uses DDR memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.
Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed in one second. This is worked out by multiplying the total number of texture units by the core speed of the chip. The better this number, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.
Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly record to its local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.