Consider the following processor design characteristics:
- Register-to-register arithmetic operations only
- Fixed-length instruction format
- Hardwired control unit
Which of the characteristics above are used in the design of a RISC processor?
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Answer: D
A RISC (Reduced Instruction Set Computer) processor is designed to simplify the instruction set to achieve high performance, primarily through efficient pipelining. The given characteristics relate to RISC as follows:
- I. Register-to-register arithmetic operations only: In RISC, only
LOADandSTOREinstructions access memory. All arithmetic and logical operations are performed strictly between processor registers. This simplifies the instruction cycle and memory interface. - II. Fixed-length instruction format: RISC instructions typically have a fixed length (e.g., 32 bits). This makes instruction fetching and decoding extremely simple and predictable, which is essential for effective pipelining.
- III. Hardwired control unit: Since RISC instructions are simple and uniform, they can be executed directly by hardware without the overhead of microprogramming. A hardwired control unit is much faster and is a key feature of RISC architectures.
Thus, all three characteristics (I, II, and III) are fundamental to the design of a RISC processor.
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