ppl:CPI≈1？铁律？ Program execution 200 400 600 800 1000 1200 1400 Time order (in instructions) 1dx1,100(x4) Instruction fetch Reg ALU Data 图4-25 access Reg Data 1dx2,200(x4) 200ps Instruction ALU fetch Reg access Reg Data 1dx3.400(x4) 200ps Instruction fetch Reg ALU access Reg 200ps200ps200ps 200ps200ps Memory CPU G UE bu3 VO bue Memory VO devicea Registere e Disk memory Regiater Cache Memory reference reference referenoe reference Size:500 bytee 64KB 1 GB 1TB Speed: 250pa 1n8 100n8 10 meppl：CPI ≈ 1？铁律？ 图4-25