Modern CPU architecture consists of dozens of registers and register sets, each having it's own important purpose. Majority of registers that modern architectures have aren't even documented, and unless they're documented officially by the manufacturer, it is very hard or sometimes impossible to debug or analyze these registers even for the best-skilled reverse-engineers.

In this short article I'd like to cover some of the most used and best documented registers that serve very important role in today's modern computing.

SIMD

Single instruction, multiple data is a type of parallel processing that supports parallel computation. The computation is divided into different units, each performing the exact same task. This can greatly improve performance, especially when doing the same computation for many different objects.

The classic example of this type of computing would be changing the brightness of a monitor, where every RGB value of every pixel has to be incremented by some same amount. Other typical applications are sound or image encoding, graphics processing or signal processing.