Comparison between Hardwired and Microprogrammed Control Units

Comparison between Hardwired and Microprogrammed Control Units

Hardwired control

Speed: Fast

Control functions: Implemented in hardware

Flexibility: Not flexible, to accommodate new system specifications or new instructions.

Ability to handle large/complex instruction sets: Somewhat difficult

Ability to support operating systems and diagnostic features: Very difficult (unless Easy anticipated during design)

Design process: Somewhat complicated

Applications: Mostly RISC microprocessors

Instruction set size: Usually under 100 instructions

ROM size: -

Chip area efficiency: Uses least area

Microprogrammed control

Speed: Slow

Control functions: Implemented in software

Flexibility: More flexible, to accommodate new system specification or new instructions redesign is required.

Ability to handle large/complex instruction sets: Easier

Ability to support operating systems and diagnostic features: Easy

Design process: Processor Design

Ability to support operating systems and diagnostic features: Orderly and systematic

Applications: Mainframes, some microprocessors

Instruction set size: Usually over 100 instructions

ROM size: 2 K to 10 K by 20-400 bit microinstructions

Chip area efficiency: Uses more area

Review Question

1. Compare hardwired control unit with microprogrammed control unit.