Compare any two graphics cards:
GeForce GT 640 DDR3 vs Radeon HD 4850 2GB
IntroThe GeForce GT 640 DDR3 comes with a clock frequency 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 is comprised of 384 SPUs, 32 TAUs, and 16 Raster Operation Units.
Compare all that to the Radeon HD 4850 2GB, which comes with a clock frequency of 625 MHz and a GDDR4 memory frequency of 993 MHz. It also uses a 256-bit memory bus, and uses a 55 nm design. It is made up of 800(160x5) SPUs, 40 Texture Address Units, and 16 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The Radeon HD 4850 2GB should theoretically be a bit faster than the GeForce GT 640 DDR3 overall. (explain)
Texel RateThe GeForce GT 640 DDR3 is just a bit (approximately 15%) better at texture filtering than the Radeon HD 4850 2GB. (explain)
Pixel RateIf using high levels of AA is important to you, then the GeForce GT 640 DDR3 is a better choice, by far. (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 information (measured in megabytes per second) that can be transported over the external memory interface in one second. It is calculated by multiplying the card's bus width by the speed of its memory. In the case of DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.
Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be processed in one second. This number is calculated by multiplying the total texture units of the card by the core clock speed of the chip. The higher this number, the better the 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 the video card can possibly write to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.