Compare any two graphics cards:
Radeon HD 4830 512MB vs Radeon HD 6770 1GB
IntroThe Radeon HD 4830 512MB comes with a core clock speed of 575 MHz and a GDDR3 memory frequency of 900 MHz. It also features a 256-bit bus, and uses a 55 nm design. It is comprised of 640(128x5) SPUs, 32 Texture Address Units, and 16 Raster Operation Units.
Compare that to the Radeon HD 6770 1GB, which has a clock speed of 900 MHz and a GDDR5 memory speed of 1050 MHz. It also uses a 128-bit memory bus, and uses a 40 nm design. It is comprised of 800 SPUs, 40 TAUs, and 16 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The Radeon HD 6770 1GB should in theory be a little bit faster than the Radeon HD 4830 512MB overall. (explain)
Texel RateThe Radeon HD 6770 1GB will be a lot (about 96%) better at AF than the Radeon HD 4830 512MB. (explain)
Pixel RateIf using a high resolution is important to you, then the Radeon HD 6770 1GB is superior to the Radeon HD 4830 512MB, by a large margin. (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 (counted in MB per second) that can be transported across the external memory interface in a second. The number is calculated by multiplying the bus width by the speed of its memory. If it uses DDR type memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.
Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This figure is calculated by multiplying the total texture units of the card by the core 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 in a second.
Pixel Rate: Pixel rate is the maximum amount of pixels the video card could possibly write to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.