Compare any two graphics cards:
GeForce GT 640 DDR3 vs Radeon HD 4850 2GB
IntroThe GeForce GT 640 DDR3 uses a 28 nm design. nVidia has clocked the core frequency at 900 MHz. The DDR3 memory runs at a speed of 1782 MHz on this particular model. It features 384 SPUs along with 32 TAUs and 16 Rasterization Operator Units.
Compare those specifications to the Radeon HD 4850 2GB, which makes use of a 55 nm design. AMD has set the core speed at 625 MHz. The GDDR4 RAM is set to run at a speed of 993 MHz on this specific model. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 ROPs.
(No game benchmarks for this combination yet.)
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
Theoretically, the Radeon HD 4850 2GB should perform a small bit faster than the GeForce GT 640 DDR3 in general. (explain)
Texel RateThe GeForce GT 640 DDR3 will be just a bit (more or less 15%) more effective at texture filtering than the Radeon HD 4850 2GB. (explain)
Pixel RateIf using lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is the winner, 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 max amount of data (measured in MB per second) that can be moved over the external memory interface in one second. It's calculated by multiplying the card's bus width by the speed of its memory. If the card has DDR RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen 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 by the core clock 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 most pixels the graphics card can possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of ROPs by the the core 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 output rate also depends on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.