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.
- 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.
- 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
|Microprogrammed 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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