Compare any two graphics cards:
GeForce 9800 GT 1GB vs GeForce GT 640 DDR3
IntroThe GeForce 9800 GT 1GB makes use of a 65/55 nm design. nVidia has set the core frequency at 600 MHz. The GDDR3 RAM is set to run at a frequency of 900 MHz on this model. It features 112 SPUs along with 56 Texture Address Units and 16 Rasterization Operator Units.
Compare all that to the GeForce GT 640 DDR3, which has a GPU core clock 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)
Theoretically, the GeForce 9800 GT 1GB should be a small bit faster than the GeForce GT 640 DDR3 in general. (explain)
Texel RateThe GeForce 9800 GT 1GB will be a bit (more or less 17%) more effective at AF than the GeForce GT 640 DDR3. (explain)
Pixel RateThe GeForce GT 640 DDR3 will be much (about 50%) better at anti-aliasing than the GeForce 9800 GT 1GB, and able to handle higher 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 data (measured in megabytes per second) that can be moved across the external memory interface in a second. The number is worked out by multiplying the card's interface width by the speed of its memory. In the case of DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the better 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 applied in one second. This number is calculated by multiplying the total texture units by the core clock speed of the chip. The higher the texel rate, the better the 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 amount of pixels that the graphics card can possibly record to the local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate also depends on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.