Compare any two graphics cards:
GeForce 8500 GT vs GeForce GT 640 DDR3
IntroThe GeForce 8500 GT features a GPU 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 is made up of 16 Stream Processors, 8 Texture Address Units, and 4 Raster Operation Units.
Compare all that to the GeForce GT 640 DDR3, which makes use of a 28 nm design. nVidia has clocked the core speed at 900 MHz. The DDR3 RAM works at a speed of 1782 MHz on this particular model. It features 384 SPUs along with 32 Texture Address Units and 16 ROPs.
(No game benchmarks for this combination yet.)
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
In theory, the GeForce GT 640 DDR3 is 346% quicker than the GeForce 8500 GT overall, due to its greater data rate. (explain)
Texel RateThe GeForce GT 640 DDR3 will be a lot (about 700%) better at texture filtering than the GeForce 8500 GT. (explain)
Pixel RateIf running with a high screen resolution is important to you, then the GeForce GT 640 DDR3 is a better choice, 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.
Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.
Memory Bandwidth: Bandwidth is the maximum amount of information (counted in megabytes per second) that can be moved past the external memory interface within a second. It's worked out by multiplying the bus width by its memory clock speed. In the case of DDR type memory, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.
Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be processed in one second. This number is worked out by multiplying the total number of texture units 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 per second.
Pixel Rate: Pixel rate is the maximum number 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 number of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.