Question

Advantages and disadvantages of microprogrammed control unit

Answer 1

What are the advantages and disadvantages of microprogrammed control unit comparedto hardwired control unit? Explain why hardwired control unit is usually used for RISCand microprogrammed control unit for CISC architectures.Advantages:-The decoders and sequencing logic unit of a micro-programmed control unit are verysimple pieces of logic, compared to the hardwired control unit, which contains complexlogic for sequencing through the many micro-operations of the instruction cycle. Itsimplifies the design of the control unit. Simpler design means the control unit ischeaper and less error-prone to implement-It is also flexible as changes could be easily made to the designPrincipal Disadvantage:-Slower than a hardwired unit of comparable technologyHardwired control unit is used for RISC Architecture because hardwired is faster and canimprove the performanceMicroprogrammed control unit is used for CISC because it makes the design simpler andusually in CISC architecture, due to huge number of instructions in the instruction set, thecontrol unit is quite complex. Hence it justifies using microprogrammed control unit