Compare any two graphics cards:
GeForce GT 640 DDR3 vs GeForce GTX 650
IntroThe GeForce GT 640 DDR3 has a clock speed of 900 MHz and a DDR3 memory speed of 1782 MHz. It also uses a 128-bit memory bus, and makes use of a 28 nm design. It is comprised of 384 SPUs, 32 Texture Address Units, and 16 ROPs.
Compare all that to the GeForce GTX 650, which makes use of a 28 nm design. nVidia has set the core frequency at 1058 MHz. The GDDR5 memory works at a speed of 1250 MHz on this specific model. It features 384 SPUs along with 32 TAUs and 16 Rasterization Operator Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The GeForce GTX 650 should in theory be a lot faster than the GeForce GT 640 DDR3 in general. (explain)
Texel RateThe GeForce GTX 650 will be a little bit (more or less 18%) faster with regards to AF than the GeForce GT 640 DDR3. (explain)
Pixel RateIf using a high screen resolution is important to you, then the GeForce GTX 650 is a better choice, though not by far. (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 max amount of data (measured in MB per second) that can be moved over the external memory interface in a second. It's calculated by multiplying the card's bus width by the speed of its memory. If the card has DDR memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the faster 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 are processed in one second. This number is worked out by multiplying the total texture units of the card by the core speed of the chip. The higher this number, 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 amount of pixels that the graphics chip can possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.