Instruction Length:

• Variable-length instructions (Intel 80x86, VAX) need multi-step fetch and decode, but permit for a much more flexible and compressed instruction set.
• Fixed-length instructions permit easy fetch and decode, and simplify parallelism and pipelining.

All of the MIPS instructions are 32 bits long.

-this decision put effect on every other ISA decision we make because it build instruction bits scarce.

 MIPS instruction format

• The opcode tells the machine which format
• So add r1,r2,r3 has

-        Opcode=0, funct=32,rs=2,rt=3,rd=1,sa=0

-        000000   00010  00011 00001 0000 100000