Lec06a - COMP 4300 Computer Architecture Multicycle...

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1 COMP 4300 Computer Architecture Multicycle Implementation Dr. Xiao Qin Auburn University http://www.eng.auburn.edu/~xqin xqin@auburn.edu Fall, 2010
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2 The Problem with Single-Cycle Processor Implementation: Performance Performance is limited by the slowest instruction Example: suppose we have the following delays Memory read/write 200ps ALU and adders 100ps Register File read/write 50ps What is the critical path for each instruction?
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3 What is the critical path for lw? lw: 200 + 50 + 100 + 200 + 50 600ps P C address Inst. R1 (rt) R2 (rs) -100 lw ReadRegister#1 ReadRegister#2 WriteRegister Data Port#1 Port#2 ALU REGISTERS ROM Instruction Memory Data Memory RAM DataIn Address DataOut 16 (Imm) SIGN-EXTEND 16 32 Memory read/write 200ps ALU and adders 100ps Register File read/write 50ps
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4 sw R1, -100(R2) P C address Inst. R1 R2 -100 sw ReadRegister#1 ReadRegister#2 WriteRegister Data Port#1 Port#2 ALU REGISTERS ROM Instruction Memory Data Memory RAM DataIn Address DataOut 16 SIGN-EXTEND 16 32 What is the critical path for sw? Memory read/write 200ps ALU and adders 100ps Register File read/write 50ps Sign-Extended 10ps
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5 sw R1, -100(R2) P C address Inst. R1 R2 -100 sw ReadRegister#1 ReadRegister#2 WriteRegister Data Port#1 Port#2 ALU REGISTERS ROM Instruction Memory Data Memory RAM DataIn Address DataOut 16 SIGN-EXTEND 16 32 Memory read/write 200ps ALU and adders 100ps Register File read/write 50ps sw: 200 + 50 + 100 + 200 550ps What is the critical path for sw?
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6 What is the critical path for each instruction? R-format 200 + 50 + 100 + 0 + 50 400ps Load word 200 + 50 + 100 + 200 + 50 600ps Store word 200 + 50 + 100 + 200 550ps Branch 200 + 50 + 100 350ps Jump 200 200ps What is the implication?
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7 Alternatives to Single-Cycle Multicycle Processor Implementation Shorter clock cycle Multiple clock cycles per instruction
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This note was uploaded on 12/07/2011 for the course COMP 3400 taught by Professor Staff during the Fall '10 term at Auburn University.

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Lec06a - COMP 4300 Computer Architecture Multicycle...

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