ISA: Types

Types of architectures

CISC: complex instruction set computer

Traditional computer architecture

Unique instructions for as many operations as possible

Advantages

Each instruction can do more work

Programs use less memory

Easier to program directly or to write compilers

Disadvantages

More complex hardware circuits

More expensive to develop and build

Usually slower

RISC: reduced instruction set computer

Developed from research in late '70's/early '80's at IBM, Stanford, and UC-Berkeley

Look at actual instruction use, focus on most frequent ones

Advantages

Easier to learn

Simpler circuits

Cheaper and more reliable to design and build

Faster

Disadvantages

Larger, more complex programs

Harder to program

Depends on compiler for optimization