Question

Which one of the following characteristics is correct regarding RISC processor ?
1. Relatively very large addressing modes
2. Multi-cycle instruction execution
3. All operations are not done within the registers of the CPU
4. Relatively few instructions
5.

Answer 1

Correct Answer - Option 1 : Relatively very large addressing modes

Combinational logic units, which have a finite number of gates and can create specified outputs dependent on the instructions used to activate those responses, are used to implement hardwired control units. Their design is based on a fixed architecture, which requires wiring adjustments if the instruction set is updated or modified. In computers with a small instruction set, this design is preferable (RISC).
The main idea is to simplify hardware by using an instruction set consisting of a few basic steps for loading, evaluating, and storing operations, similar to how a load command loads data and a store command stores it.
RISC processors provide very few addressing modes: often just one or two. A large Number of Registers: Since RISC processors use register-to-register operations, we need to have a large number of registers.

 

Characteristic of RISC – 

1. Simpler instruction, hence simple instruction decoding. 
2. Instruction comes undersize of one word. 
3. Instruction takes a single clock cycle to get executed.
4. More general-purpose registers. 
5. Simple Addressing Modes. 
6. Fewer Data types. 
7. The pipeline can be achieved.

RISC	CISC
Reduced Instruction Set Architecture	Complex Instruction Set Architecture
Focus on software	Focus on hardware
Uses only Hardwired control unit	Uses both hardwired and microprogrammed control unit
Transistors are used for more registers	Transistors are used for storing complex  Instructions
Fixed sized instructions	Variable sized instructions
Can perform only Register to Register Arithmetic operations­	Can perform REG to REG or REG to MEM or MEM to MEM
Requires more number of registers	Requires less number of registers
Code size is large	Code size is small
An instruction executed in a single clock cycle	Instruction takes more than one clock cycle