Compare any two graphics cards:
Radeon HD 4730 vs Radeon HD 6770 1GB
IntroThe Radeon HD 4730 has a GPU clock speed of 700 MHz, and the 512 MB of GDDR5 memory is set to run at 900 MHz through a 128-bit bus. It also is comprised of 640(128x5) Stream Processors, 32 TAUs, and 8 Raster Operation Units.
Compare that to the Radeon HD 6770 1GB, which comes with GPU clock speed of 900 MHz, and 1024 MB of GDDR5 RAM set to run at 1050 MHz through a 128-bit bus. It also is made up of 800 Stream Processors, 40 TAUs, and 16 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
In theory, the Radeon HD 6770 1GB is 17% faster than the Radeon HD 4730 overall, because of its higher bandwidth. (explain)
Texel RateThe Radeon HD 6770 1GB is a lot (about 61%) faster with regards to AF than the Radeon HD 4730. (explain)
Pixel RateIf running with a high screen resolution is important to you, then the Radeon HD 6770 1GB 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 largest amount of data (measured in megabytes per second) that can be transferred past the external memory interface in a second. It is calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR RAM, the result should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher 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 figure is worked out by multiplying the total texture units by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.
Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly record to the local memory in a second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Render Output Units by the the card's clock speed. 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 rate is also dependant on quite a few other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.