Compare any two graphics cards:
GeForce GTX 460 vs Radeon HD 4890 1GB
IntroThe GeForce GTX 460 has a GPU core speed of 675 MHz, and the 768 MB of GDDR5 RAM runs at 900 MHz through a 192-bit bus. It also is made up of 336 SPUs, 56 Texture Address Units, and 24 ROPs.
Compare all that to the Radeon HD 4890 1GB, which comes with a core clock speed of 1000 MHz and a GDDR5 memory speed of 975 MHz. It also makes use of a 256-bit memory bus, and uses a 55 nm design. It is comprised of 800(160x5) SPUs, 40 TAUs, and 16 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The Radeon HD 4890 1GB should theoretically perform a lot faster than the GeForce GTX 460 in general. (explain)
Texel RateThe Radeon HD 4890 1GB will be a small bit (about 6%) more effective at texture filtering than the GeForce GTX 460. (explain)
Pixel RateThe GeForce GTX 460 is just a bit (about 1%) more effective at FSAA than the Radeon HD 4890 1GB, and also 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 (counted in MB per second) that can be transferred across the external memory interface in one second. It's worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR type memory, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.
Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be processed per second. This is calculated by multiplying the total texture units by the core clock speed of the chip. The higher 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 amount of pixels that the graphics card can possibly write to its local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the number of Render Output Units by the the card's clock speed. 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 also depends on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.