Instruction register
In computing a is instruction register (short IR) is part of a CPU - control plant that stores the instructions that are being executed or decoded. In simple processors, every instruction that is to be executed is loaded into the instruction register and stored there until it is decoded, prepared and finally executed - which can take several steps.
Some of the more complicated processes take advantage of an instruction pipeline , with each section of the pipeline doing some of the decoding, preparing, and executing, and then passing it on to the next section for the next step. Modern processors can even process some steps completely independently of the actual sequence, e.g. B. perform the decoding of several instructions in parallel.
Decoding the opcode in the instruction register includes determining the instruction, determining where the operands are in memory, fetching these operands from memory, allocating processor resources to execute the instruction (e.g. in super scalar processors) etc.
The output of IRs is available to control circuitry to generate the clock signals in which the various processing elements involved in executing the instruction.
In the instruction cycle , the instruction is loaded into the instruction register after the processor fetches it from the memory location determined by the instruction counter .
Individual evidence
- ↑ John L. Hennessy and David A. Patterson : Computer Architecture: a quantitative approach . Morgan Kaufmann Publishers, Palo Alto 1990, 784 pp., ISBN 1-55860-069-8
- ^ M. Morris Mano: Computer System Architecture . 3rd edition, Prentice Hall 1992, 525 pp., ISBN 0-13-175563-3