Compare any two graphics cards:
GeForce 9800 GT 1GB vs GeForce GT 640 DDR3
IntroThe GeForce 9800 GT 1GB has core speeds of 600 MHz on the GPU, and 900 MHz on the 1024 MB of GDDR3 memory. It features 112 SPUs along with 56 TAUs and 16 ROPs.
Compare those specifications to the GeForce GT 640 DDR3, which features GPU core speed of 900 MHz, and 2048 MB of DDR3 memory set to run at 1782 MHz through a 128-bit bus. It also features 384 SPUs, 32 TAUs, and 16 Raster Operation Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
In theory, the GeForce 9800 GT 1GB should be 1% quicker than the GeForce GT 640 DDR3 in general, because of its higher data rate. (explain)
Texel RateThe GeForce 9800 GT 1GB should be a little bit (about 17%) more effective at texture filtering than the GeForce GT 640 DDR3. (explain)
Pixel RateThe GeForce GT 640 DDR3 will be a lot (more or less 50%) more effective at FSAA than the GeForce 9800 GT 1GB, and also should be capable of handling higher screen resolutions without slowing down too much. (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: Memory bandwidth is the largest amount of information (in units of MB per second) that can be moved past the external memory interface in one second. It's worked out by multiplying the card's interface width by the speed of its memory. If the card has 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 AA, HDR and high resolutions.
Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are processed 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 higher the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one 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 figure is worked out by multiplying the number of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate is also dependant on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.