Smáforritunarlíkan

Smáforritunarlíkan is an Icelandic term that translates to "microprogramming model." It refers to a specific approach in computer architecture where the control unit of a processor is itself controlled by a small program, known as a microprogram. Instead of having hardwired logic to execute instructions, the processor fetches instructions from a control store, which contains sequences of microinstructions. Each microinstruction specifies the elementary operations (micro-operations) to be performed by the processor's datapath.

This model allows for greater flexibility in processor design. Complex machine instructions can be implemented as sequences of simpler microinstructions. This makes it easier to design and modify instruction sets, as changes can be made by altering the microprogram rather than redesigning the entire hardware. It also facilitates the implementation of features like microcode updates to fix bugs or add new capabilities after the hardware has been manufactured.

The process involves fetching a machine instruction from memory. This instruction is then used as an address or part of an address to look up the corresponding microprogram in the control store. The microprogram is then executed, step by step, by the processor's datapath. Each step in the microprogram signals which internal components of the CPU should be activated and what data transfers should occur.

While microprogramming offers flexibility, it can sometimes be slower than hardwired control due to the overhead of fetching and interpreting microinstructions. However, for complex instruction sets or for processors requiring a high degree of adaptability, the microprogramming model has been a significant architectural choice. It was particularly prevalent in earlier processor designs but continues to be relevant in specialized architectures.