1. Computer Architecture 6001215-3 Lec 06: Computer Architecture Introduction

2. Why Learn Computer Architecture?  You want to call yourself a “computer scientist” l Computer architecture impacts every other aspect of computer science  You need to make a purchasing decision or offer “expert” advice  You want to build software people use – sell many, many copies- (need performance) l Both hardware and software affect performance -Algorithm determines number of source-level statements -Language/compiler/architecture determine machine instructions (Chapter 2 and 3) -Processor/memory determine how fast instructions are executed (Chapter 5, 6, and 7) -Assessing and understanding performance(Chapter 4)

3. l Design better programs, including system software such as compilers, operating systems, and device drivers. l Optimize program behavior. l Evaluate (benchmark) computer system performance. l Understand time, space, and price tradeoffs. Why study computer organization and architecture?

4. Computer Architecture vs Computer Organization  Computer organization l Encompasses all physical aspects of computer systems. l E.g., circuit design, control signals, memory types. l How does a computer work?  Computer architecture l Logical aspects of system implementation as seen by the programmer. l E.g., instruction sets, instruction formats, data types, addressing modes. l How do I design a computer?

5. Computer Systems  Software l Application software – Word Processors, Email, Internet Browsers, Games l Systems software – Compilers, Operating Systems  Hardware l CPU l Memory l I/O devices (mouse, keyboard, display, disks, networks,……..)

6. How Do the Pieces Fit Together?  Coordination of many levels of abstraction  Under a rapidly changing set of forces  Design, measurement, and evaluation I/O systemInstr. Set Proc. Compiler Operating System Application Digital Design Circuit Design Instruction Set Architecture Firmware Memory system Datapath & Control

7. instruction set software hardware  One of the most important abstractions is ISA l A critical interface between HW and SW l Example: MIPS l Desired properties -Convenience (from software side) -Efficiency (from hardware side) Instruction Set Architecture (ISA)

8.  ISA: An abstract interface between the hardware and the lowest level software of a machine that encompasses all the information necessary to write a machine language program that will run correctly, including instructions, registers, memory access, I/O, and so on. “... the attributes of a [computing] system as seen by the programmer, i.e., the conceptual structure and functional behavior, as distinct from the organization of the data flows and controls, the logic design, and the physical implementation.” – Amdahl, Blaauw, and Brooks, 1964 l Enables implementations of varying cost and performance to run identical software  ABI (application binary interface): The user portion of the instruction set plus the operating system interfaces used by application programmers. Defines a standard for binary portability across computers.

9. High-level to Machine Language High-level language program (in C) Assembly langMIPSuage program (for) Binary machine language program (for MIPS) Compiler Assembler

10. Organization of a computer

11. Anatomy of Computer Personal Computer Processor Computer Control (“brain”) Datapath (“brawn”) Memory (where programs, data live when running) Devices Input Output Keyboard, Mouse Display, Printer Disk (where programs, data live when not running) 5 classic components Datapath: performs arithmetic operation Control: guides the operation of other components based on the user instructions

12. Moore’s Law  In 1965, Gordon Moore predicted that the number of transistors that can be integrated on a die would double every 18 to 24 months (i.e., grow exponentially with time).  Amazingly visionary – million transistor/chip barrier was crossed in the 1980’s. l 2300 transistors, 1 MHz clock (Intel 4004) - 1971 l 16 Million transistors (Ultra Sparc III) l 42 Million transistors, 2 GHz clock (Intel Xeon) – 2001 l 55 Million transistors, 3 GHz, 130nm technology, 250mm 2 die (Intel Pentium 4) - 2004 l 140 Million transistor (HP PA-8500)

13. Moore’s Law  “Cramming More Components onto Integrated Circuits” l Gordon Moore, Electronics, 1965  # of transistors per cost-effective integrated circuit doubles every 18 months “Transistor capacity doubles every 18-24 months” Speed 2x / 1.5 years (since ‘85); 100X performance in last decade

14. Trend: Microprocessor Performance

15. Example Machine Organization  Workstation design target l 25% of cost on processor l 25% of cost on memory (minimum memory size) l Rest on I/O devices, power supplies, box CPU Computer Control Datapath MemoryDevices Input Output

16. Consider this advertisement: An ExampleExample System MHz?? MB?? PCI?? USB?? L1 Cache?? What does it all mean??

17. Standards Organizations  There are many organizations that set computer hardware standards-- to include the interoperability of computer components.  Throughout this book, and in your career, you will encounter many of them.  Some of the most important standards-setting groups are...

18. Standards Organizations  The Institute of Electrical and Electronic Engineers (IEEE) l Promotes the interests of the worldwide electrical engineering community. l Establishes standards for computer components, data representation, and signaling protocols, among many other things.

19. Standards Organizations  The International Telecommunications Union (ITU) l Concerns itself with the interoperability of telecommunications systems, including data communications and telephony.  National groups establish standards within their respective countries: l The American National Standards Institute (ANSI) l The British Standards Institution (BSI)

20. Standards Organizations  The International Organization for Standardization (ISO) l Establishes worldwide standards for everything from screw threads to photographic film. l Is influential in formulating standards for computer hardware and software, including their methods of manufacture. Note: ISO is not an acronym. ISO comes from the Greek, isos, meaning “equal.”

21. The Computer Level Hierarchy  Computers consist of many things besides chips.  Before a computer can do anything worthwhile, it must also use software.  Writing complex programs requires a “divide and conquer” approach, where each program module solves a smaller problem.  Complex computer systems employ a similar technique through a series of virtual machine layers.

22. The Computer Level Hierarchy  Each virtual machine layer is an abstraction of the level below it.  The machines at each level execute their own particular instructions, calling upon machines at lower levels to perform tasks as required.  Computer circuits ultimately carry out the work.

23. The Computer Level Hierarchy  Level 6: The User Level l Program execution and user interface level. l The level with which we are most familiar.  Level 5: High-Level Language Level l The level with which we interact when we write programs in languages such as C, Pascal, Lisp, and Java.

24. The Computer Level Hierarchy  Level 4: Assembly Language Level l Acts upon assembly language produced from Level 5, as well as instructions programmed directly at this level.  Level 3: System Software Level l Controls executing processes on the system. l Protects system resources. l Assembly language instructions often pass through Level 3 without modification.

25. The Computer Level Hierarchy  Level 2: Machine Level l Also known as the Instruction Set Architecture (ISA) Level. l Consists of instructions that are particular to the architecture of the machine. l Programs written in machine language need no compilers, interpreters, or assemblers.

26. The Computer Level Hierarchy  Level 1: Control Level l A control unit decodes and executes instructions and moves data through the system. l Control units can be microprogrammed or hardwired. l A microprogram is a program written in a low- level language that is implemented by the hardware. l Hardwired control units consist of hardware that directly executes machine instructions.

27. The Computer Level Hierarchy  Level 0: Digital Logic Level l This level is where we find digital circuits (the chips). l Digital circuits consist of gates and wires. l These components implement the mathematical logic of all other levels.

28. The von Neumann Model  Today’s stored-program computers have the following characteristics: l Three hardware systems: -A central processing unit (CPU) -A main memory system -An I/O system l The capacity to carry out sequential instruction processing. l A single data path between the CPU and main memory. -This single path is known as the von Neumann bottleneck.

29. The von Neumann Model  This is a general depiction of a von Neumann system:  These computers employ a fetch- decode-execute cycle to run programs as follows...