Compare any two graphics cards:
GeForce 8600 GT 1GB DDR2 vs Radeon HD 4550 256MB
IntroThe GeForce 8600 GT 1GB DDR2 has clock speeds of 540 MHz on the GPU, and 400 MHz on the 1024 MB of DDR2 RAM. It features 32 SPUs along with 16 TAUs and 8 ROPs.
Compare all that to the Radeon HD 4550 256MB, which makes use of a 55 nm design. AMD has set the core speed at 600 MHz. The DDR3 RAM is set to run at a frequency of 800 MHz on this particular model. It features 80(16x5) SPUs along with 8 TAUs and 4 Rasterization Operator Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Both cards have the exact same bandwidth, so in theory they should have identical performance. (explain)
Texel RateThe GeForce 8600 GT 1GB DDR2 should be a lot (approximately 80%) faster with regards to AF than the Radeon HD 4550 256MB. (explain)
Pixel RateIf running with a high screen resolution is important to you, then the GeForce 8600 GT 1GB DDR2 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: Bandwidth is the maximum amount of information (counted in MB per second) that can be transferred across the external memory interface within a second. It is worked out by multiplying the card's interface width by its memory clock speed. If it uses DDR type memory, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. 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 applied in one second. This number is calculated by multiplying the total texture units by the core clock speed of the chip. The better the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.
Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly record to the local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Raster Operations Pipelines by the clock speed of the card. 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 fill rate also depends on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.