HARDWIRED CONTROL UNIT. MICROPROGRAMMED CONTROL UNIT. The control unit whose control signals are generated by the hardware through a. Hardwired control units are implemented through use of control units are generally faster than microprogrammed. The main difference between Hardwired and Microprogrammed Control Unit is that a Hardwired Control Unit is a sequential circuit that.

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Tomasulo algorithm Reservation station Re-order buffer Register renaming. The Control Unit can either be hardwired or microprogrammed. The control unit CU is a component of a computer’s central processing unit CPU that directs the ,icroprogrammed of the processor.

Difference Between Hardwired and Microprogrammed Control Unit

As it is hardwired, the instruction set is constant and does not change. The CU receives external instructions or commands which it converts into a sequence of control signals that the CU applies to the data path to implement a sequence of register-transfer level operations. On some processors, the Control Unit may be further broken down into additional units, such as an instruction unit or scheduling unit to handle scheduling, or a retirement unit to deal with results coming from the instruction pipeline.

Hardwired Control Unit is a unit that uses combinational logic units, featuring a finite number of gates that can generate specific results based on microlrogrammed instructions that were used to invoke those responses. In Microprogrammed Control Unit, modifications can be implemented by changing the microinstructions in the control memory.

This architecture is preferred in reduced instruction set computers RISC as they use a simpler instruction ccontrol. Branch prediction Memory dependence prediction. From Wikipedia, the free encyclopedia. The control memory contains control words. Microprogrammed Control Unit is a unit that contains microinstructions in the control memory to produce control signals. These microinstructions refer to a control word that resides in unkt memory, containing control signals for execution of micro-operations.

The circuit uses a fixed architecture. Hardwired Control Unit is implemented using various electronic components such as combinational logic units and gates. On the other hand, Microprogrammed Control Units are easier to modify, decode, implement and capable of handling complex instructions. Overall, these control units have a simple structure.


The speed of operations in Hardwired Control Unit is fast. Views Read Edit View history. Outputs of the controller are organized in microinstructions and they can be easily replaced. It consists of main two subsystems: A controller that uses this approach can operate at high speed; however, it has little flexibility, and the complexity of the instruction set it can implement is limited.

A control word is a set of ones and zeros in a control variable.

Control unit

John von Neumann included the control unit as part of the von Neumann architecture. More precisely, the Control Unit CU is generally a sizable collection of complex digital circuitry interconnecting and directing the many execution units i.

Therefore, Microptogrammed Control Unit is more flexible. Most computer resources are managed by the CU.


Previously, control units for CPUs used ad-hoc logic, and they were difficult to design. However, Hardwired Control Units are difficult to modify and implement.

Moreover, hardsired is difficult to perform instruction decoding in Hardwired Control Unit than in Microprogrammed Control Unit. The result of these routed data movements through various digital circuits sub-units within the processor produces the manipulated data expected by a software instruction loaded earlier, likely from memory.

Archived from the original on Hardwired control units are generally faster than microprogrammed designs. It tells the computer’s memory, arithmetic and logic unit and input and output devices how to respond to the instructions that have been sent to the processor.

The Control unit CU is digital circuitry contained within the processor that coordinates the sequence of data wnd into, out of, and between a processor’s many sub-units. Data dependency Structural Control False sharing.

In additon to the above differences, the Hardwired Control Unit uses a small instruction set while theMicroprogrammed Control Unit uses a large instruction set. ALU handles the mathematical and logical operations while CU sends timing and control signals to the other units to synchronize the tasks.


By using this site, you agree to the Terms of Use and Privacy Policy. It is also difficult to add new features to the existing design. Other more advanced forms of Control Units manage the translation of instructions but not the data containing portion into several micro-instructions and the CU manages the scheduling of the micro-instructions between the selected execution units to which the data is then channeled and changed according to the execution unit’s function i.

It directs the operation of the other units by providing timing and control signals. This CU instruction decode process is then repeated when the Program Counter is incremented to the next stored program address and the new instruction enters the CU from that address, and so on till the programs end.

The idea of microprogramming was introduced by Maurice Wilkes in as an intermediate level to execute computer program instructions. Also, there is no control memory usage in Hardwired Yardwired Unit but, on the other hand, Microprogrammed Control Unit uses control memory. This article is about the component of a computer’s CPU. Basic Structure of the Computer.

The processor or the CPU is hardwirwd main component of the computer that handles most of the tasks. Computer Organization and Design: Their design uses a fixed architecture—it requires changes in the wiring if the instruction set is modified or changed. Hardwired control units are implemented through use of combinational logic units, featuring a finite number of gates that can generate mcroprogrammed results based on the instructions that were used to invoke those responses.

Therefore, it has minimum flexibility. Synthesis of compositional microprogram control units for programmable devices. Single-core Multi-core Manycore Heterogeneous architecture. This page was last edited on 20 Decemberat Processor register Register file Memory buffer Program counter Stack.