RISC [Reduced Instruction Set Computer]

• RISC processors only use simple instructions that can be executed within one clock cycle.
• Thus, the "MULT" command described above could be divided into three separate commands: 
• "LOAD," which moves data from the memory bank to a register,
• "PROD," which finds the product of two operands located within the registers
• "STORE," which moves data from a register to the memory banks. 

                        LOAD A, 2:3

                      LOAD B, 5:2

                      PROD A, B

                      STORE 2:3, A

• More RAM is needed to store the assembly level instructions.
• The compiler must also perform more work to convert a high-level language statement into machine code. 
• To execute each instruction, if there is separate electronic circuitry in the control unit, which produces all the necessary signals.
• It is also called hard-wired approach. 
• pipelining: a techique that allows for simultaneous execution of parts, or stages, of instructions to more efficiently process instructions; 
• large number of registers:
• Examples of RISC processors: 
• IBM RS6000, MC88100 
• DEC’s Alpha 21064, 21164 and 21264 processors 

Features of RISC Processors: 

• RISC processors use a small and limited number of instructions.
• RISC machines mostly uses hardwired control unit. 
• RISC processors consume less power and are having high performance. 
• Each instruction is very simple and consistent. 
• RISC processors uses simple addressing modes. 
• RISC instruction is of uniform fixed length.