MS108 Computer System I Lecture 2 Metrics Prof. Xiaoyao Liang 2014/2/28 1

Performance Metrics 2

3

CPI 4

IPC 5

IPC 6

Amdahl’s Law 7

8

9

Performance Equation 10 The Processor Performance Equation

11 Performance Equation

12 Different instruction types having different CPIs

13MIPS

14MFLOPS

15GHz

16

17

18 IC Cost Cost driven down by learning curve –Yield DRAM: price closely tracks cost Microprocessors: price depends on volume –10% less for each doubling of volume

IC Cost 19 Integrated circuit Bose-Einstein formula: Defects per unit area = defects per square cm (2010) N = process-complexity factor = (40 nm, 2010)

IC Cost 20

Availability Year 21

Power 22

Power 23

Power 24 Dynamic energy –Transistor switch from 0 -> 1 or 1 -> 0 –½1/2 x Capacitive load x Voltage 2 Dynamic power –½ 1/2x Capacitive load x Voltage 2 x Frequency switched Reducing clock rate reduces power, not energy

Power 25 Static power consumption –Current static x Voltage –Scales with number of transistors –To reduce: power gating

Power 26 Intel consumed ~ 2 W 3.3 GHz Intel Core i7 consumes 130 W Heat must be dissipated from 1.5 x 1.5 cm chip This is the limit of what can be cooled by air

Benchmark 27

Benchmark 28

29Benchmark