Compare any two graphics cards:
GeForce GT 340 vs GeForce GT 340 1GB
IntroThe GeForce GT 340 has a core clock frequency of 550 MHz and a GDDR5 memory frequency of 850 MHz. It also uses a 128-bit memory bus, and uses a 40 nm design. It is made up of 96 SPUs, 32 Texture Address Units, and 8 ROPs.
Compare those specifications to the GeForce GT 340 1GB, which features a GPU core clock speed of 550 MHz, and 1024 MB of GDDR5 RAM running at 850 MHz through a 128-bit bus. It also features 96 SPUs, 32 Texture Address Units, and 8 Raster Operation Units.
Power Usage and Theoretical BenchmarksBoth cards have the same power consumption.
Both cards have exactly the same memory bandwidth, so theoretically they should perform exactly the same. (explain)
Texel RateBoth cards have exactly the same texel fill rate, so theoretically they should be equally good at at AF. (explain)
Pixel RateBoth cards have exactly the same pixel fill rate, so theoretically they should be equally good at at full screen anti-aliasing, and be capable of handling the same screen resolutions. (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 information (in units of MB per second) that can be transported across the external memory interface in a second. The number is worked out by multiplying the bus width by its memory speed. If it uses DDR type RAM, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the bandwidth is, the faster 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 are processed in one second. This is worked out by multiplying the total texture units by the core speed of the chip. The better this number, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.
Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly record to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on lots of other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.