Difference between Hardwired and Micro-programmed Control Unit | Set 2

Prerequisite – Hardwired v/s Micro-programmed Control Unit
To execute an instruction, there are two types of control units Hardwired Control unit and Micro-programmed control unit.

  1. Hardwired control units are generally faster than microprogrammed designs. In hardwired control, we saw how all the control signals required inside the CPU can be generated using a state counter and a PLA circuit.
  2. A microprogrammed control unit is a relatively simple logic circuit that is capable of (1) sequencing through microinstructions and (2) generating control signals to execute each microinstruction.
Hardwired Control Unit Microprogrammed Control Unit
Hardwired control unit generates the control signals needed for the processor using logic circuits Micrprogrammed control unit generates the control signals with the help of micro instructions stored in control memory
Hardwired control unit is faster when compared to microprogrammed control unit as the required control signals are generated with the help of hardwares This is slower than the other as micro instructions are used for generating signals here
Difficult to modify as the control signals that need to be generated are hard wired Easy to modify as the modification need to be done only at the instruction level
More costlier as everything has to be realized in terms of logic gates Less costlier than hardwired control as only micro instructions are used for generating control signals
It cannot handle complex instructions as the circuit design for it becomes complex It can handle complex instructions
Only limited number of instructions are used due to the hardware implementation Control signals for many instructions can be generated
Used in computer that makes use of Reduced Instruction Set Computers(RISC) Used in computer that makes use of Complex Instruction Set Computers(CISC)

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