Microcode

The microcodes is a program made up of Micro-instruction S whose execution within the Processeur or Microprocesseur defines the Instruction set of this one.

Microcodes is in the center of microprogramed architectures. On those, the computer code -- (macro) - instructions -- are interpreted by microcodes which controls in its turn the internal elements with the processor, such as for example the Arithmetic logic unit (ALUMINUM), etc It is thus necessary to carry out a great number of microinstructions for one (macro) - instruction.

There are two techniques of implementation of microcodes:

  1. microcodes It horizontal , which will use a very broad number of bits to control all the elements of the processor. On the IBM 360 model 30 for example, a microinstruction makes 60 bits.
  2. microcodes It vertical , which will occupy much less bits because it will contain a part specifying the unit to be controlled, and another which will be the order sent to this unit.

In the case of microcoded microprocessors microcodes it will be stored in a ROMANIAN intern with the Integrated circuit, whereas in the case of a processor it will be simply put in a ROMANIAN, sometimes associated with a RAM.

The architectures based on bit-slice microprocessors are microcoded, it is established with dimensions Microphone-sequencer, person in charge of its unfolding.

Advantages and disadvantages of the microcoded machines

  • the advantages are (inter alia):
  • : evolutionarity of the instruction sets
  • : simplicity of the design
  • : possible correction of the errors of design material by modification of microcodes
  • the disadvantages are (inter alia):
  • : possibilities of bug S in microcodes
  • : slowness of the machine

Example of microcoded computers

See too

  • the term Microsoftware, which more generally indicates an integrated software in an electronics component.

External bonds

  • has Brief History Microprogramming off (in English).

  • Wang 2200 Microarchitecture Description (in English).

Simple: Microprogram

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