Shader basics
Today’s GPUs are powerful computing units. While the main job of older graphics cards was just to display the graphics memory (consisting of 2D images of the windows and their contents), the evolution to 3D has shifted some tasks from the CPU to the GPU.
The main “workhorses” in a GPU are the shader units. These are small and simple processing units with a limited instruction set, compared to the system processor. However, they utilize large registers and can operate on more than one data value at once, calculating multiple results in a single step. This is called Single Instruction, Multiple Data (SIMD). You may also have heard terms such as SSE as being included in your CPU (older readers may also remember the predecessors, MMX and 3DNow!). With SIMD, each one of the registers can load more than one value, usually two or four of them. Mathematical operations, such as multiplication or addition, are done on each pair of values in two registers...
