Compare any two graphics cards:
GeForce GTX 960 vs Radeon HD 4870 2GB
IntroThe GeForce GTX 960 features clock speeds of 1127 MHz on the GPU, and 1750 MHz on the 2048 MB of GDDR5 memory. It features 1024 SPUs as well as 64 Texture Address Units and 32 Rasterization Operator Units.
Compare those specifications to the Radeon HD 4870 2GB, which has core speeds of 750 MHz on the GPU, and 900 MHz on the 2048 MB of GDDR5 memory. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 Rasterization Operator Units.
Power Usage and Theoretical Benchmarks
Power Consumption (Max TDP)
The Radeon HD 4870 2GB should in theory be a bit faster than the GeForce GTX 960 overall. (explain)
Texel RateThe GeForce GTX 960 is much (approximately 140%) more effective at anisotropic filtering than the Radeon HD 4870 2GB. (explain)
Pixel RateIf using high levels of AA is important to you, then the GeForce GTX 960 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.
Memory Bandwidth: Bandwidth is the max amount of information (measured in MB per second) that can be transported over the external memory interface in a second. It's worked out by multiplying the interface width by its memory clock speed. If the card has DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.
Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed in one second. This is worked out by multiplying the total number of texture units of the card by the core speed of the chip. The higher the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.
Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly record to its local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Raster Operations Pipelines by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.