Compare any two graphics cards:
GeForce 8600 GT 512MB GDDR3 vs GeForce 9500 GT 1GB GDDR3
IntroThe GeForce 8600 GT 512MB GDDR3 has a GPU core clock speed of 540 MHz, and the 512 MB of GDDR3 RAM is set to run at 700 MHz through a 128-bit bus. It also features 32 SPUs, 16 TAUs, and 8 ROPs.
Compare those specifications to the GeForce 9500 GT 1GB GDDR3, which has a GPU core clock speed of 550 MHz, and 1024 MB of GDDR3 memory running at 800 MHz through a 128-bit bus. It also features 32 SPUs, 16 Texture Address Units, and 8 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Theoretically, the GeForce 9500 GT 1GB GDDR3 should be a bit faster than the GeForce 8600 GT 512MB GDDR3 overall. (explain)
Texel RateThe GeForce 9500 GT 1GB GDDR3 is a small bit (about 2%) better at texture filtering than the GeForce 8600 GT 512MB GDDR3. (explain)
Pixel RateIf running with lots of anti-aliasing is important to you, then the GeForce 9500 GT 1GB GDDR3 is superior to the GeForce 8600 GT 512MB GDDR3, though not by far. (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 information (in units of MB per second) that can be transported across the external memory interface within a second. The number is worked out by multiplying the card's interface width by its memory clock speed. If it uses DDR type RAM, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.
Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied per second. This is calculated by multiplying the total number of texture units by the core clock speed of the chip. The higher this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.
Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card could possibly write to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.