Hardwired control unit and Micro-programmed control unit

Difference between hardwired control unit and micro-programmed control unit:

Hardwired Control Unit

• In the hardwired organization, the control logic is implemented with gates, flip-flops, decoders, and other digital circuits.

• A hardwired control, as the name implies, requires changes in the wiring among the various components if the design has to be modified or changed.

• Difficult to design, test and implement.

• Faster mode of operation.

• It is expensive to implement and more error prone.

• Typically used in RISC processor.

      Micro-programmed Control Unit

•  In the micro-programmed organization, the control information is stored in a control memory, and uses sequence of micro-instructions to generate control signals.

•  In the microprogramming control, any required changes or modifications can be done by updating the microprogram in control memory; thus is more flexible.

• Easy to design, test and implement.

•  Slower mode of operation.

• Cheaper and less error prone.

• Typically used in CISC processor.

Computer Organization And Architecture

Difference Between Computer Organization and Architecture

• Computer architecture refers to those parameters of a computer system that are visible to a programmer or those parameters that have a direct impact on the logical execution of a program. Examples of architectural attributes include the instruction set, the number of bits used to represent different data types, I/O mechanisms, and addressing techniques.

• Computer organization refers to the operational units and their interconnections that implement the architectural specifications. Examples of organizational attributes include those hardware details transparent to the programmer such as control signals, interfaces between the computer and peripherals, and the memory technology used.

• Architecture describes what the computer does and Organization describes how it does it.

• For example, it is an architectural design issue whether a computer will have a multiply instruction. It is an organizational issue whether that instruction will be implemented by a special multiply unit or by a mechanism that makes repeated use of the add unit of the system.

• A particular computer architecture may span over many years and can have number of different computer models. Organization changes with changing technology.

• Architecture and organization are independent; you can change the organization of a computer without changing its architecture. For example, a 64-bit architecture can be internally organized as a true 64-bit machine or as a 16-bit machine that uses four cycles to handle 64-bit values. Programs written to run on a particular computer architecture should always run correctly on that architecture no matter what computer organization (implementation) is used.