Compare any two graphics cards:
GeForce GTS 450 vs Radeon HD 4850 2GB
IntroThe GeForce GTS 450 features a GPU clock speed of 783 MHz, and the 512 MB of GDDR5 memory runs at 902 MHz through a 128-bit bus. It also is made up of 192 Stream Processors, 32 Texture Address Units, and 16 ROPs.
Compare all that to the Radeon HD 4850 2GB, which features a GPU core clock speed of 625 MHz, and 2048 MB of GDDR4 RAM running at 993 MHz through a 256-bit bus. It also is comprised of 800(160x5) SPUs, 40 TAUs, and 16 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Theoretically speaking, the Radeon HD 4850 2GB should perform just a bit faster than the GeForce GTS 450 overall. (explain)
Texel RateThe GeForce GTS 450 is a little bit (more or less 0%) more effective at texture filtering than the Radeon HD 4850 2GB. (explain)
Pixel RateIf using a high resolution is important to you, then the GeForce GTS 450 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.
Memory Bandwidth: Memory bandwidth is the max amount of data (measured in megabytes per second) that can be moved over the external memory interface in one second. It is calculated by multiplying the card's interface width by the speed of its memory. In the case of DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the better 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 amount of texture map elements (texels) that can be processed per second. This number is worked out by multiplying the total amount of texture units of the card by the core speed of the chip. The better the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.
Pixel Rate: Pixel rate is the most pixels the graphics card can possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.