ESE 345 Lecture Notes - Lecture 4: Instruction Set, Complex Instruction Set Computing, Arithmetic Shift
27 Dec 2020
School
Department
Course
Professor
Document Summary
The early trend was to add more and more instructions to do elaborate operations - this became known as complex instruction set computing (cisc) Opposite philosophy began to dominate: reduced instruction set computing (risc) Simpler and smaller instruction set makes it easier to build fast hardware. Let software do the complicated operations by composing simpler one. Fixed instruction length: simplifies fetching instructions from memory. Simplified addressing modes: simplifies fetching operands from memory. Few and simple instructions in the instruction set: simplifies instruction execution. Minimize memory access instructions (load/store): simplifies necessary hardware for memory access. Let compiler do heavy lifting: breaks complex statements into multiple assembly instructions. In high level languages, number of variables limited only by available memory. Isas have a fixed small number of operands called registers. Drawback: operations can only be performed on these predetermined number of registers. Mips has 32 general purpose registers (r0-31) Each register is 32 bits wife and holds a word.
