CSE 305. Computer Architecture

Transcription

1 CSE 305 Computer Architecture

2 Computer Architecture Course Teachers Rifat Shahriyar Johra Muhammad Moosa Textbook Computer Orgaizatio ad Desig (The Hardware/Software Iterface) David A. Patterso ad Joh L. Heessy (5 th Ed.) Homepage

3 Chapter 1 Computer Abstractios ad Techology

4 The Computer Revolutio Progress i computer techology Uderpied by Moore s Law Makes ovel applicatios feasible 1.1 Itroductio Computers i automobiles Cell phoes Huma geome project World Wide Web Search Egies Computers are pervasive Chapter 1 Computer Abstractios ad Techology 4

5 Moore s Law The umber of trasistors i a dese itegrated circuit doubles approximately every two years Named after Gordo Moore, the co-fouder of Itel described a doublig every year revised the forecast to doublig every two years The period is ofte quoted as 18 moths Chapter 1 Computer Abstractios ad Techology 5

6 Moore s Law Chapter 1 Computer Abstractios ad Techology 6

7 Classes of Computers Persoal computers Geeral purpose, variety of software Subject to cost/performace tradeoff Server computers Network based High capacity, performace, reliability Rage from small servers to buildig sized Chapter 1 Computer Abstractios ad Techology 7

8 Classes of Computers Supercomputers High-ed scietific ad egieerig calculatios Highest capability but represet a small fractio of the overall computer market Embedded computers Hidde as compoets of systems Striget power/performace/cost costraits Chapter 1 Computer Abstractios ad Techology 8

9 The PostPC Era Chapter 1 Computer Abstractios ad Techology 9

10 The PostPC Era Persoal Mobile Device (PMD) Battery operated Coects to the Iteret Hudreds of dollars Smart phoes, tablets, electroic glasses Cloud computig Warehouse Scale Computers (WSC) Software as a Service (SaaS) Portio of software ru o a PMD ad a portio ru i the Cloud Amazo ad Google Chapter 1 Computer Abstractios ad Techology 10

11 What You Will Lear How programs are traslated ito the machie laguage Ad how the hardware executes them The hardware/software iterface What determies program performace Ad how it ca be improved How hardware desigers improve performace What is parallel processig Chapter 1 Computer Abstractios ad Techology 11

12 Uderstadig Performace Algorithm Determies umber of operatios executed Programmig laguage, compiler, architecture Determie umber of machie istructios executed per operatio Processor ad memory system Determie how fast istructios are executed I/O system (icludig OS) Determies how fast I/O operatios are executed Chapter 1 Computer Abstractios ad Techology 12

13 Eight Great Ideas Desig for Moore s Law Use abstractio to simplify desig Make the commo case fast Performace via parallelism Performace via pipeliig Performace via predictio Hierarchy of memories 1.2 Eight Great Ideas i Computer Architecture Depedability via redudacy Chapter 1 Computer Abstractios ad Techology 13

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15 Below Your Program Applicatio software Writte i high-level laguage System software Compiler: traslates HLL code to machie code Operatig System: service code Hardware Hadlig iput/output Maagig memory ad storage Schedulig tasks & sharig resources Processor, memory, I/O cotrollers 1.3 Below Your Program Chapter 1 Computer Abstractios ad Techology 15

16 Levels of Program Code High-level laguage Level of abstractio closer to problem domai Provides for productivity ad portability Assembly laguage Textual represetatio of istructios Hardware represetatio Biary digits (bits) Ecoded istructios ad data Chapter 1 Computer Abstractios ad Techology 16

17 The BIG Picture Same compoets for all kids of computer Desktop, server, embedded 1.4 Uder the Covers Compoets of a Computer Iput/output icludes User-iterface devices Storage devices Display, keyboard, mouse Hard disk, CD/DVD, flash Network adapters For commuicatig with other computers Chapter 1 Computer Abstractios ad Techology 17

18 Aatomy of a Computer Output device Network cable Iput device Iput device Chapter 1 Computer Abstractios ad Techology 18

19 Aatomy of a Mouse Optical mouse LED illumiates desktop Small low-res camera Basic image processor Looks for x, y movemet Buttos & wheel Supersedes roller-ball mechaical mouse Chapter 1 Computer Abstractios ad Techology 19

20 Through the Lookig Glass LCD scree: picture elemets (pixels) Mirrors cotet of frame buffer memory Chapter 1 Computer Abstractios ad Techology 20

21 Touchscree PostPC device Supersedes keyboard ad mouse Resistive ad Capacitive types Most tablets, smart phoes use capacitive Capacitive allows multiple touches simultaeously Chapter 1 Computer Abstractios ad Techology 21

22 Opeig the Box Capacitive multitouch LCD scree 3.8 V, 25 Watt-hour battery Computer board Chapter 1 Computer Abstractios ad Techology 22

23 Iside the Processor (CPU) Datapath: performs operatios o data Cotrol: sequeces datapath, memory, I/O devices... Cache memory Small fast SRAM memory for immediate access to data Chapter 1 Computer Abstractios ad Techology 23

24 Iside the Processor Apple A5 Chapter 1 Computer Abstractios ad Techology 24

25 Iside the Processor AMD Barceloa: 4 processor cores Chapter 1 Computer Abstractios ad Techology 25

26 Iside the Processor Northbridge ad Southbridge Chapter 1 Computer Abstractios ad Techology 26

27 Iside the Processor Northbridge ad Southbridge Chapter 1 Computer Abstractios ad Techology 27

28 Abstractios The BIG Picture Abstractio helps us deal with complexity Hide lower-level detail Istructio set architecture (ISA) The hardware/software iterface Applicatio biary iterface The ISA plus system software iterface Implemetatio The details uderlyig ad iterface Chapter 1 Computer Abstractios ad Techology 28

29 Abstractios Problem Operatig System Iterface betwee Software Architecture ad Hardware Circuits Chapter 1 29

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31 A Safe Place for Data Volatile mai memory Loses istructios ad data whe power off No-volatile secodary memory Magetic disk Flash memory Optical disk (CDROM, DVD) Chapter 1 Computer Abstractios ad Techology 31

32 Networks Commuicatio ad resource sharig Local area etwork (LAN): Etheret Withi a buildig Wide area etwork (WAN: the Iteret Wireless etwork: WiFi, Bluetooth Chapter 1 Computer Abstractios ad Techology 32

33 Techology Treds Electroics techology cotiues to evolve Icreased capacity ad performace Reduced cost DRAM capacity Year Techology Relative performace/cost 1951 Vacuum tube Trasistor Itegrated circuit (IC) Very large scale IC (VLSI) 2,400, Ultra large scale IC 250,000,000, Techologies for Buildig Processors ad Memory Chapter 1 Computer Abstractios ad Techology 33

34 Defiig Performace Which airplae has the best performace? 1.6 Performace Boeig 777 Boeig 777 Boeig 747 BAC/Sud Cocorde Douglas DC-8-50 Boeig 747 BAC/Sud Cocorde Douglas DC Passeger Capacity Cruisig Rage (miles) Boeig 777 Boeig 777 Boeig 747 BAC/Sud Cocorde Douglas DC-8-50 Boeig 747 BAC/Sud Cocorde Douglas DC Cruisig Speed (mph) Passegers x mph Chapter 1 Computer Abstractios ad Techology 34

35 Respose Time ad Throughput Respose time How log it takes to do a task Idividual computer users iterest Throughput Total work doe per uit time (tasks per hour) Dataceter maagers iterest How are respose time ad throughput affected by Replacig the processor with a faster versio Addig additioal processors to a system that uses multiple processors for separate tasks Chapter 1 Computer Abstractios ad Techology 35

36 Relative Performace Defie Performace = 1/Executio Time X is time faster tha Y Performace Performace X Y = Executio time Y Executio time X = Example: time take to ru a program 10s o A, 15s o B Executio Time B / Executio Time A = 15s / 10s = 1.5 So A is 1.5 times faster tha B Chapter 1 Computer Abstractios ad Techology 36

37 Measurig Executio Time Wall Clock time/elapsed time Total respose time, icludig all aspects Processig, I/O, OS overhead, idle time Determies system performace CPU time Time spet processig a give job Discouts I/O time, other jobs shares Comprises user CPU time ad system CPU time Differet programs are affected differetly by CPU ad system performace Chapter 1 Computer Abstractios ad Techology 37

38 CPU Clockig Operatio of digital hardware govered by a costat-rate clock Clock period Clock (cycles) Data trasfer ad computatio Update state Clock period: duratio of a clock cycle e.g., 250ps = 0.25s = s Clock frequecy (rate): cycles per secod e.g., 4.0GHz = 4000MHz = Hz Chapter 1 Computer Abstractios ad Techology 38

39 CPU Time CPU Time = CPU Clock Cycles Clock Cycle Time Performace improved by = CPU Clock Cycles Clock Rate Reducig umber of clock cycles Icreasig clock rate Hardware desiger must ofte trade off clock rate agaist cycle cout May techiques that decrease the umber of clock cycles may also icrease the clock cycle time Chapter 1 Computer Abstractios ad Techology 39

40 CPU Time Example Computer A: 2GHz clock, 10s CPU time Desigig Computer B Aim for 6s CPU time Ca do faster clock, but causes 1.2 clock cycles How fast must Computer B clock be? Clock Rate B = Clock Cycles CPU Time B B = 1.2 Clock Cycles 6s A Clock Cycles A = CPU Time A Clock Rate A = 10s 2GHz = Clock Rate B = s 9 = s 9 = 4GHz Chapter 1 Computer Abstractios ad Techology 40

41 Istructio Cout ad CPI Clock Cycles = Istructio Cout Cycles per Istructio CPU Time = Istructio Cout CPI Clock Cycle Time Istructio Cout for a program Determied by program, ISA ad compiler Average cycles per istructio Determied by CPU hardware If differet istructios have differet CPI Istructio Cout CPI = Clock Rate Average CPI affected by istructio mix Chapter 1 Computer Abstractios ad Techology 41

42 CPI Example Computer A: Cycle Time = 250ps, CPI = 2.0 Computer B: Cycle Time = 500ps, CPI = 1.2 Same ISA Which is faster, ad by how much? CPU Time A CPU Time B CPU Time B CPU Time A = Istructio Cout CPI A = I ps = I 500ps = Istructio Cout CPI Cycle Time B B = I ps = I 600ps I 600ps = I 500ps = 1.2 Cycle Time A A is faster by this much Chapter 1 Computer Abstractios ad Techology 42

43 CPI i More Detail If differet istructio classes take differet umbers of cycles Clock Cycles = å i= 1 (CPIi Istructio Cout i) Weighted average CPI CPI = Clock Cycles Istructio Cout = å i= 1 æ çcpi è i Istructio Cout i Istructio Cout ö ø Relative frequecy Chapter 1 Computer Abstractios ad Techology 43

44 CPI Example Chapter 1 Computer Abstractios ad Techology 44

45 CPI Example Alterative compiled code sequeces usig istructios i classes A, B, C Class A B C CPI for class IC i sequece IC i sequece Sequece 1: IC = 5 Clock Cycles = = 10 Avg. CPI = 10/5 = 2.0 Sequece 2: IC = 6 Clock Cycles = = 9 Avg. CPI = 9/6 = 1.5 Chapter 1 Computer Abstractios ad Techology 45

46 Performace Summary The BIG Picture CPU Time = Secods Program = Istructios Program Performace depeds o Clock cycles Istructio Secods Clock cycle Algorithm: affects IC, possibly CPI Programmig laguage: affects IC, CPI Compiler: affects IC, CPI Istructio set architecture: affects IC, CPI, T c Chapter 1 Computer Abstractios ad Techology 46

47 Chapter 1 Computer Abstractios ad Techology 47

48 Power Treds 1.7 The Power Wall I CMOS IC techology Power = Capacitive load Voltage 2 Frequecy Chapter 1 Computer Abstractios ad Techology 48

49 Reducig Power Suppose a ew CPU has 85% of capacitive load of old CPU 15% voltage ad 15% frequecy reductio P 4 2 ew Cold 0.85 (Vold 0.85) Fold 0.85 = = 0.85 = 2 P C V F old The power wall old We ca t reduce voltage further We ca t remove more heat old How else ca we improve performace? old 0.52 Chapter 1 Computer Abstractios ad Techology 49

50 Power vs. Performace Chapter 1 Computer Abstractios ad Techology 50

51 Uiprocessor Performace Costraied by power, istructio-level parallelism, memory latecy 1.8 The Sea Chage: The Switch to Multiprocessors Chapter 1 Computer Abstractios ad Techology 51

52 Multiprocessors Multicore microprocessors More tha oe processor per chip Requires explicitly parallel programmig Compare with istructio level parallelism Hardware executes multiple istructios at oce Hidde from the programmer Hard to do Programmig for performace Load balacig Optimizig commuicatio ad sychroizatio Chapter 1 Computer Abstractios ad Techology 52

53 SPEC CPU Bechmark Programs used to measure performace Supposedly typical of actual workload Stadard Performace Evaluatio Corp (SPEC) Develops bechmarks for CPU, I/O, Web, SPEC CPU2006 Elapsed time to execute a selectio of programs Negligible I/O, so focuses o CPU performace Normalize relative to referece machie Summarize as geometric mea of performace ratios CINT2006 (iteger) ad CFP2006 (floatig-poit) 1.9 SPEC CPU Bechmark ÕExecutio timeratio i i= 1 Chapter 1 Computer Abstractios ad Techology 53

54 CINT2006 for Itel Core i7 920 Chapter 1 Computer Abstractios ad Techology 54

55 Pitfall: Amdahl s Law Improvig a aspect of a computer ad expectig a proportioal improvemet i overall performace T improvemet affected T improved = + factor uaffected Example: multiply accouts for 80s/100s How much improvemet i multiply performace to get 5 overall? = + 20 Ca t be doe! T 1.10 Fallacies ad Pitfalls Corollary: make the commo case fast Chapter 1 Computer Abstractios ad Techology 55

56 Fallacy: Low Power at Idle Look back at i7 power bechmark At 100% load: 258W At 50% load: 170W (66%) At 10% load: 121W (47%) Google data ceter Mostly operates at 10% 50% load At 100% load less tha 1% of the time Cosider desigig processors to make power proportioal to load Chapter 1 Computer Abstractios ad Techology 56

57 Pitfall: MIPS as a Performace Metric MIPS: Millios of Istructios Per Secod Does t accout for MIPS = = Differeces i ISAs betwee computers Differeces i complexity betwee istructios Istructio cout Executio time 10 Istructio cout Istructio cout CPI 10 Clock rate 6 6 Clock rate = 6 CPI 10 CPI varies betwee programs o a give CPU Chapter 1 Computer Abstractios ad Techology 57

58 Pitfall: MIPS as a Performace Metric Computer A 10 Billio istructios, 4GHz Clock rate CPI = 1 Computer B 8 Billio istructios, 4GHz Clock rate CPI = 1.1 1) Which has the highest MIPS ratig? 2) Which is faster? Chapter 1 Computer Abstractios ad Techology 58

59 Cocludig Remarks Cost/performace is improvig Due to uderlyig techology developmet Hierarchical layers of abstractio I both hardware ad software Istructio set architecture The hardware/software iterface Executio time: the best performace measure Power is a limitig factor Use parallelism to improve performace 1.11 Cocludig Remarks Chapter 1 Computer Abstractios ad Techology 59