Compare any two graphics cards:
GeForce GT 420 vs Radeon HD 4850 X2 1GB
IntroThe GeForce GT 420 comes with core clock speeds of 700 MHz on the GPU, and 900 MHz on the 2048 MB of GDDR3 memory. It features 48 SPUs as well as 8 TAUs and 4 ROPs.
Compare those specs to the Radeon HD 4850 X2 1GB, which has a GPU core clock speed of 625 MHz, and 1024 MB of GDDR3 RAM set to run at 993 MHz through a 256-bit bus. It also features 800(160x5) Stream Processors, 40 Texture Address Units, and 16 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The Radeon HD 4850 X2 1GB should in theory perform much faster than the GeForce GT 420 overall. (explain)
Texel RateThe Radeon HD 4850 X2 1GB is a lot (about 793%) more effective at AF than the GeForce GT 420. (explain)
Pixel RateIf running with lots of anti-aliasing is important to you, then the Radeon HD 4850 X2 1GB is the winner, 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.
One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.
Memory Bandwidth: Bandwidth is the max amount of data (measured in MB per second) that can be transferred past the external memory interface within a second. It's worked out by multiplying the bus width by its memory clock speed. If it uses DDR RAM, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the memory bandwidth, 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 number of texture map elements (texels) that are processed per second. This is calculated by multiplying the total 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 in a second.
Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly write to its local memory per second - measured in millions of pixels per second. The figure 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 filling the screen with pixels (the image). The actual pixel rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.