Types of instruction set

Types of Instruction Sets

CISC (Complex Instruction Set Computing)

• Characteristics:
  • Complex instructions that can perform multiple tasks.
  • Instructions can take multiple clock cycles to execute.
  • Large number of instructions and addressing modes.
• Examples: x86, x87.

RISC (Reduced Instruction Set Computing)

• Characteristics:
  • Simple instructions that can be combined to perform complex tasks.
  • Instructions typically execute in a single clock cycle.
  • Small number of instructions and addressing modes.
• Examples: ARM, PowerPC, SPARC.

EPIC (Explicitly Parallel Instruction Computing)

• Characteristics:
  • Instructions are explicitly parallel, allowing for more efficient execution.
  • Compiler plays a crucial role in scheduling instructions.
• Examples: IA-64 (Itanium).

VLIW (Very Long Instruction Word)

• Characteristics:
  • Instructions are packed into long words, allowing for multiple operations to be specified in a single instruction.
  • Compiler plays a crucial role in scheduling instructions.
• Examples: Some DSPs (Digital Signal Processors).

Comparison

• CISC vs RISC: CISC instructions are more complex, while RISC instructions are simpler and more efficient.
• RISC vs EPIC/VLIW: RISC focuses on simple instructions, while EPIC and VLIW focus on parallel execution and compiler-scheduled instructions.