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Hard-wired Control Unit v/s Soft-wired Control Unit
written 5.9 years ago by | modified 2.1 years ago by |
what is the difference between hardwired and softwired contro unit?
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written 5.9 years ago by | modified 2.1 years ago by |
what is the difference between hardwired and softwired contro unit?
written 2.1 years ago by |
Sr. No. | Parameters | Hard-wired Control Unit | Soft-wired Control Unit |
---|---|---|---|
1. | Control Signal Generation | This unit generates the control signals needed for the processor using combinational logic units, featuring a finite number of gates. | This unit generates the control signals with the help of microinstructions stored in the control memory. |
2. | Design | Its design is complex. | Its design is simplified. |
3. | Approach | It is a circuit-based approach. | It is a programming-based approach. |
4. | Architecture and Instruction Set | The architecture and instruction sets are not specified. | The architecture and instruction sets are specified. |
5. | Main Processing Unit | It has a processor to create signals to be executed in the right sequence. | It facilitates the micro-sequencer from which instruction bits are decoded and executed. |
6. | Speed | This unit is faster because the required control signals are generated with the help of hardwires. | This is slower because microinstructions are used for generating signals and also require frequent memory accesses. |
7. | Flexibility in Modification | Modification is difficult as the control unit is hardwired and will require a change in hardware. | Modifications are easy as they will require the change in the code at the instruction level only. |
8 | Chip Area | It requires less area for chips. | It requires more area for the chip. |
9. | Cost | More costly as everything has to be realized in terms of logic gates. | Less costly because only microinstructions are used for generating control signals. |
10. | Complex Instructions | It cannot handle complex instructions as the circuit design for it becomes complex. | It can handle complex instructions. |
11. | Instruction Set Size | It uses only a limited number of instruction sets due to the hardwired implementation. | Control signals for many instruction sets can be generated. |
12. | Instruction Decoding | In this, it is very difficult to perform instruction decoding and sequencing logic. | In this, it is very easy to perform instruction decoding and sequencing logic. |
13. | Control Memory | There is no control memory usage hence, no control memory is required. | This unit uses control memory hence, control memory is required. |
14. | Method | It uses either mechanical or electrical ways to control things. | It always uses digital ways to control things. Means it has a computer or simpler table-driven calculator with software. |
15 | Error Occurrence | More prone to the occurrence of errors. | Less prone to the occurrence of errors. |
16. | Applications | It is used in processors that use a simple instruction set known as the Reduced Instruction Set Computers (RISC). | It is used in processors based on a complex instruction set known as Complex Instruction Set Computer (CISC). |
17. | Examples | CPU with hardwired control unit is Intel 8085, Motorola 6802, Zilog 80, any RISC CPUs, in a car the steering wheel, and Power Steering system. | CPU with microprogrammed control unit is Intel 8080, Motorola 6800, any CISC CPUs, and Today's fighter jets |