Compare any two graphics cards:
GeForce 8500 GT vs Radeon HD 5450
IntroThe GeForce 8500 GT features a GPU core clock speed of 450 MHz, and the 512 MB of DDR2 RAM is set to run at 400 MHz through a 128-bit bus. It also features 16 Stream Processors, 8 Texture Address Units, and 4 Raster Operation Units.
Compare those specifications to the Radeon HD 5450, which comes with a core clock speed of 650 MHz and a DDR3 memory speed of 800 MHz. It also uses a 64-bit bus, and uses a 40 nm design. It is comprised of 80(16x5) SPUs, 8 Texture Address Units, and 4 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Both cards have exactly the same memory bandwidth, so in theory they should perform exactly the same. (explain)
Texel RateThe Radeon HD 5450 is much (about 44%) more effective at AF than the GeForce 8500 GT. (explain)
Pixel RateIf using a high resolution is important to you, then the Radeon HD 5450 is superior to the GeForce 8500 GT, by far. (explain)
Memory Bandwidth: Memory bandwidth is the largest amount of data (in units of MB per second) that can be transferred over the external memory interface within a second. It's worked out by multiplying the bus width by its memory speed. In the case of DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster 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 number of texture map elements (texels) that are applied in one second. This is worked out by multiplying the total amount of 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 processed in one second.
Pixel Rate: Pixel rate is the most pixels the graphics card can possibly write to its local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the amount of Raster Operations Pipelines 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 fill rate also depends on quite a few 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.