Compare any two graphics cards:
GeForce 8600 GT 512MB DDR2 vs Radeon HD 5450
IntroThe GeForce 8600 GT 512MB DDR2 has a core clock frequency of 540 MHz and a DDR2 memory frequency of 400 MHz. It also features a 128-bit bus, and uses a 80 nm design. It features 32 SPUs, 16 TAUs, and 8 ROPs.
Compare all of that to the Radeon HD 5450, which makes use of a 40 nm design. AMD has set the core speed at 650 MHz. The DDR3 memory runs at a frequency of 800 MHz on this specific card. It features 80(16x5) SPUs as well as 8 Texture Address Units and 4 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Both cards have the exact same memory bandwidth, so theoretically they should have identical performance. (explain)
Texel RateThe GeForce 8600 GT 512MB DDR2 should be quite a bit (approximately 66%) faster with regards to AF than the Radeon HD 5450. (explain)
Pixel RateThe GeForce 8600 GT 512MB DDR2 will be quite a bit (about 66%) more effective at anti-aliasing than the Radeon HD 5450, and should be able to handle higher resolutions better. (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 largest amount of data (in units of megabytes per second) that can be transported across the external memory interface in one second. The number is worked out by multiplying the interface width by its memory speed. If the card has DDR RAM, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.
Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed per second. This figure is calculated by multiplying the total number of texture units of the card by the core clock speed of the chip. The better this number, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.
Pixel Rate: Pixel rate is the maximum number of pixels the graphics card 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 colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.