Compare any two graphics cards:
Radeon HD 4830 512MB vs Radeon HD 6770 1GB
IntroThe Radeon HD 4830 512MB makes use of a 55 nm design. AMD has set the core speed at 575 MHz. The GDDR3 RAM works at a speed of 900 MHz on this particular model. It features 640(128x5) SPUs along with 32 Texture Address Units and 16 ROPs.
Compare those specifications to the Radeon HD 6770 1GB, which features a clock speed of 900 MHz and a GDDR5 memory frequency of 1050 MHz. It also uses a 128-bit bus, and makes use of a 40 nm design. It is comprised of 800 SPUs, 40 Texture Address Units, and 16 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
As far as performance goes, the Radeon HD 6770 1GB should in theory be a little bit superior to the Radeon HD 4830 512MB overall. (explain)
Texel RateThe Radeon HD 6770 1GB should be quite a bit (approximately 96%) faster with regards to texture filtering than the Radeon HD 4830 512MB. (explain)
Pixel RateThe Radeon HD 6770 1GB will be a lot (approximately 57%) better at AA than the Radeon HD 4830 512MB, and also able to handle higher screen resolutions without losing too much performance. (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 (measured in megabytes per second) that can be moved across the external memory interface in one second. The number is calculated by multiplying the card's bus width by the speed of its memory. If the card has DDR RAM, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.
Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied per second. This figure is calculated by multiplying the total texture units by the core speed of the chip. The higher this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels per second.
Pixel Rate: Pixel rate is the most pixels the video card could possibly record to the local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.