Compare any two graphics cards:
GeForce 9800 GT 1GB vs GeForce GT 640 DDR3
IntroThe GeForce 9800 GT 1GB has clock speeds of 600 MHz on the GPU, and 900 MHz on the 1024 MB of GDDR3 RAM. It features 112 SPUs as well as 56 Texture Address Units and 16 ROPs.
Compare those specifications to the GeForce GT 640 DDR3, which uses a 28 nm design. nVidia has set the core frequency at 900 MHz. The DDR3 memory runs at a frequency of 1782 MHz on this particular card. It features 384 SPUs as well as 32 TAUs and 16 ROPs.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
As far as performance goes, the GeForce 9800 GT 1GB should theoretically be a small bit better than the GeForce GT 640 DDR3 overall. (explain)
Texel RateThe GeForce 9800 GT 1GB should be a small bit (about 17%) faster with regards to texture filtering than the GeForce GT 640 DDR3. (explain)
Pixel RateThe GeForce GT 640 DDR3 should be quite a bit (about 50%) better at anti-aliasing than the GeForce 9800 GT 1GB, and also able to handle 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 (measured in MB per second) that can be transferred past the external memory interface within a second. It is worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR type memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range 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 is calculated by multiplying the total texture units by the core speed of the chip. The higher this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.
Pixel Rate: Pixel rate is the maximum amount of pixels the video card could possibly write to its local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the number of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on lots of other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.