定義
ISA allows communcation between software & hardware
It is also a group of COMMANDS for a CPU in machine language.
one software command can use a group sets of hardware commands, like 'copy' in software can use 'add,push,pop' in Hardware.
Instruction/Commands is also called a.k.a Opcode or Operation code
Example of Opcodes:
ADD,JUMP,STORE
Two types of ISA: CISC & RISC
CISC(complex Instruction set computing):
Large number of instructions sets
RISC(Reducted Instruction Set Computing):
Lesser set of instructions
Example of CISC & RISC
CISC
A * B
MULT A,B
RISC
A * B
Load R1,A
Load R2,B
Prod A,B
Store R3,A
Different between two
Instructions Sets
CISC > RISC
CISC is emphasis on Hardware(硬體複雜軟體簡單)
RISC is emphasis on Software(硬體簡單軟體複雜)
Execution Time
CISC is Multiple No. cycle per Instruction
RISC is 1 cycle per Instruction
Conclusion:
Both are suitable at its specific applications
E.P.I.C
Explicity Parallel Instruction Computing
