Lecture 3: instructions Set In RISC Computers

Lecture 3: instructions Set In RISC Computers
By Noor Kadhum
Architecture For 2nd class- Computer Dep.
Babylon University -Sciences College For Women

RISC (Reduced Instruction Set Computer)
The computers are designed using CISC or RISC styles depending on instruction set performed by the computer. Modern processors are pretty much all RISC, so, in this lecture we focus on RISC.

The first RISC architecture, partly based on their use of load/store approach. The term RISC was coined by David Patterson of the Berkeley RISC project, although somewhat similar concepts had appeared before.


The main differences between RISC and CISC are summarized by the following points:
1- No .of instruction: in the RISC, the no. of instructions is relatively few instructions compared with CISC.

2- Length of instruction: the length of instruction is fixed in the RISC. The length of instruction of CISC computer is variable.

3- No .of addressing mode in the RiSC is relatively few compared with CISC.

4- In RISC, the decoding process is very simple. This process depends on instruction nature in CISC computers.