Compare any two graphics cards:
GeForce 8800 GTS (G80) 320MB vs Radeon HD 4850 512MB
IntroThe GeForce 8800 GTS (G80) 320MB makes use of a 90 nm design. nVidia has set the core frequency at 513 MHz. The GDDR3 memory works at a speed of 792 MHz on this card. It features 96 SPUs as well as 48 TAUs and 20 ROPs.
Compare that to the Radeon HD 4850 512MB, which features GPU clock speed of 625 MHz, and 512 MB of GDDR3 memory running at 993 MHz through a 256-bit bus. It also features 800(160x5) Stream Processors, 40 TAUs, and 16 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The Radeon HD 4850 512MB should in theory be a bit faster than the GeForce 8800 GTS (G80) 320MB overall. (explain)
Texel RateThe Radeon HD 4850 512MB should be just a bit (approximately 2%) more effective at anisotropic filtering than the GeForce 8800 GTS (G80) 320MB. (explain)
Pixel RateIf using a high resolution is important to you, then the GeForce 8800 GTS (G80) 320MB is superior to the Radeon HD 4850 512MB, but it probably won't make a huge difference. (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: Bandwidth is the max amount of data (counted in megabytes per second) that can be moved across the external memory interface in a second. The number is calculated by multiplying the bus width by its memory speed. If it uses DDR type memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.
Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed per second. This is worked out by multiplying the total texture units of the card by the core clock speed of the chip. The higher this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.
Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly record to the local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the amount of ROPs 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 rate also depends on lots of other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.