IT 252 Computer Organization and Architecture

1. IT 252Computer Organizationand Architecture Introduction Richard Helps (based on slides from Chia-Chi Teng)

2. What is computer architecture about? • Computer architecture is the study of building computer systems. • IT 252 is roughly split into four parts. • First, we will discusses instruction set architectures—the bridge between hardware and software. • Second, we introduce more advanced processor implementations. The focus is on pipelining, which is one of the most important ways to improve performance. • Next, we talk about memory systems, I/O, and how to connect it all together. • We will also introduce you to Assembly and C programming throughout the course.

3. Why should you care? • It is interesting. • You will learn how a processor actually works! • It will help you be a better system designer and integrator. • Understanding how your program is translated to assembly code lets you reason about correctness and performance. • Better understand the relationship between hardware and software • Demystify the seemingly arbitrary (e.g., bus errors, segmentation faults) • Many cool jobs require an understanding of computer architecture. • The cutting edge is often pushing computers to their limits. • Supercomputing, games, portable devices, etc. • Computer architecture illustrates many fundamental ideas in all computing discipline. • Abstraction, caching, and indirection …

4. Personnel • Lecturer • Prof. Richard Helps • Richard_helps@byu.edu • Office hours • W 12-2 PM • Or by appointment • TA • Michael Zanandrea (Labs) • thefastone11@hotmail.com • TBD (Homework) • TA Office hours • F 12-1 PM in CTB 365, or by appointment • Course webpage: http://it252.groups.et.byu.net/12fa/IT252.php

5. Administrivia • The textbooks provides the most comprehensive coverage • "Computer Systems: A Programmer's Perspective" 2nd Edition, by Randal E. Bryant & David R. O'Hallaron • The C Programming Language, Kernighan & Ritchie, 2nd ed. • Read the text prior to class • class will supplement rather than regurgitate the text • You need to do the reading. It will impact class discussion, homework, labs and tests

6. Grading • Professionalism: Attendance, Attitude, Participation, 5% final grade • Homework – Usually due on every Friday and Monday, check course website often for detail and update, 25% final grade • Quizzes – about 8, in class, 10 pts each, 15% final grade • No make-up, but drop lowest score. • Lab reports – Due date to be specified by TA, 25% final grade • Exams - final and at least one mid-term; usually open-book, take home, untimed 30%

7. Homework • Homework exercises provide added impetus to keep up with the reading. • Textbook problems plus other • Assignments are listed on course web page by weeks, usually due on Monday of the following week. • Turn in: on Gradebook • We really want to encourage discussion, both in class and in lab. • But zero tolerance for cheating, don’t go there. Don’t look for solutions online. • HW1 due two weeks from today on 9/6, due to Labor day. Start early.

8. Labs • No lab this week. Lab 1 week of 10-14 Sept. • Labs in Room 335 • Lab report: TA will give you detail

9. To-Do list • Read chapter 1 before Thursday • Please read the entire course web thoroughly, today • Course web is dynamic, please check back often • IT 252 Gradebook • check your email daily (IT252 in subject line) • keep up with the reading: this week … • homework due • Check website (again, turn in on Gradebook & on paper) • lab report due • TA discretion via Gradebook

10. What is Computer Architecture? It’s the study of the ___________ of computers • Structure: static arrangement of the parts • Organization:dynamic interaction of the parts and their control • Implementation: design of specific building blocks • Performance: behavioral study of the system or of some of its components

11. Another definition: Instruction Set Architecture (ISA) • Architecture is an interfacebetween layers • ISA is the interface between hardware and software • ISA is what is visible to the programmer (and ISA might be different for OS and applications) • ISA consists of: • instructions (operations and how they are encoded) • information units (size, how they are addressed etc.) • registers (or more generally processor state) • input-output control

12. Computer structure: Von Neumann model 1945 Data path + CPU Control Memory hierarchy control ALU I/O PC Registers state Memory bus I/O bus

13. Computer Organization • Organization and architecture often used as synonyms • Organization(in this course) refers to: • what are the basic blocks of a computer system, more specifically • basic blocks of the CPU • basic blocks of the memory hierarchy • how are the basic blocks designed, controlled, connected? • Organization used to be transparent to the ISA. • Today more and more of the ISA is “exposed” to the user/compiler.

14. 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. • 2300 transistors, 1 MHz clock (Intel 4004) - 1971 • 16 Million transistors (Ultra Sparc III) • 42 Million transistors, 2 GHz clock (Intel Xeon) – 2001 • 55 Million transistors, 3 GHz, 130nm technology, 250mm2 die (Intel Pentium 4) - 2004 • 140 Million transistors (HP PA-8500) • Today: 2.6 Billion transistors (10-core Xeon) • http://en.wikipedia.org/wiki/Transistor_count

15. Illustration of Moore’s Law • http://www.indybay.org/newsitems/2006/05/18/18240941.php

16. Power Consumption: Watt/cm^2 • http://www.anandtech.com/print/5626

17. Evolution of Microprocessor Speeds

18. Where is the Market? Millions of Computers

19. Today’s Market • Embedded: 15 billion+ devices • Desktop/Laptop: 900 million to 1 billion • Servers: Unknown specific but at least 3 million in the world, not including virtual • Sources from Intel, AMD, GE, and other.

20. Impacts of Advancing Technology • Processor • logic capacity: increases about 30% per year • performance: 2x every 1.5 years • Memory • DRAM capacity: 4x every 3 years, now 2x every 2 years • memory speed: 1.5x every 10 years • cost per bit: decreases about 25% per year • Disk • capacity: increases about 60% per year ClockCycle = 1/ClockRate 500 MHz ClockRate = 2 nsec ClockCycle 1 GHz ClockRate = 1 nsec ClockCycle 4 GHz ClockRate = 250 psec ClockCycle

21. Admin • Using the LS site

22. Example Machine Organization • Typical workstation design target • 25% of cost on processor • 25% of cost on memory (minimum memory size) • Rest on I/O devices, power supplies, box Computer CPU Memory Devices Control Input Datapath Output

23. PC Motherboard Closeup

24. Inside the Pentium 4 Processor Chip

25. Some Computer families • Computers that have the same (or very similar) ISA • Compatibility of software between various implementations • IBM • 704, 709, 70xx etc.. From 1955 till 1965 • 360, 370, 43xx, 33xx From 1965 to the present • Power PC • DEC • PDP-11, VAX From 1970 till 1985 • Alpha (now Compaq, now HP) in 1990’s

26. More computer families • Intel • Early micros 40xx in early 70’s • x86 (086,…,486, Pentium, Pentium Pro, Pentium 3, Pentium 4) from 1980 on • IA-64 (Itanium) in 2001 • SUN • Sparc, Ultra Sparc 1985 0n • MIPS-SGI • Mips 2000, 3000, 4400, 10000 from 1985 on • CISC vs RISC • Complex Instruction Set vs Reduced Instruction Set • What is an instruction?

27. Where Are We Now? CS142 & 124 IT344 Operating Sys (if used)

28. Registers • Registers are the “bricks”of the CPU • Registers are an essential part of the ISA • Visible to the hardware and to the programmer • Registers are • Used for high speed storage for operands. For example, if variables i,j are in registers ax,cx respectively add ax,cx # i = i + j • Easy to name (most computers have limited number of registers visible to the programmer) • Used for addressing memory

29. Registers (ct’d) • Not all registers are “equal” • Some are special-purpose (e.g. program counter, stack pointer) • Some are used for integer and some for floating-point • Some have restricted use by convention • Orthogonal Instruction sets • When any instruction can apply to any register or any memory address the I.S. is called “orthogonal” • Most instruction sets are “mostly” orthogonal • Learning the bits that are not orthogonal (and why) is a significant part of computer architecture

30. Memory system • Memory is a hierarchyof devices with faster and more expensive ones closer to CPU • Registers • Caches (hierarchy: on-chip, off-chip) • Main memory (DRAM) • Secondary memory (disks) CSE378 Gen. Intro

31. Information units • Basic unit is the bit(has value 0 or 1) • Bits are grouped together in units and operated on together: • Byte = 8 bits • Word = 2 or 4 bytes • Double word = 2 words • Etc. • Integer: usually 4 bytes • Note that word length depends on the architecture. • Architectures exist with 24-bit words and others. CSE378 Gen. Intro

32. Memory addressing • Memory is an array of information units • Each unit has the same size • Each unit has its own address • Address of an unit and contents of the unit at that address are different 0 -123 1 17 0 2 contents address This content could be pointing to address ‘0’

33. Addressing • In most of today’s computers, the basic unit that can be addressed is a byte.(how many bit is a byte?) • MIPS (and pretty much all CPU today) is byte addressable • The address spaceis the set of all memory units that a program can reference • The address space is usually tied to the length of the registers • Intel 384/486/Pentium has 32-bit registers. Hence its basic address space is 232 = 4G bytes • MIPS has 32-bit registers. • Older micros (minis) had 16-bit registers, hence 216 = 64 KB address space (too small) • Some current (Intel CoreX, Alpha, Itanium, Sparc, Altheon) machines have 64-bit registers, hence an enormous address space (264 = 18 ExaBytes (1018))

34. Addressing words • Although machines are byte-addressable, 4 byte integers are the most commonly used units • Every 32-bit word starts at an address divisible by 4 int at address 0 int at address 4 int at address 8

35. The CPU - Instruction Execution Cycle • The CPU executes a program by repeatedly following this cycle 1. Fetch the next instruction, say instruction i 2. Execute instruction i 3. Compute address of the next instruction, say j 4. Go back to step 1 • Of course we’ll optimize this but it’s the basic concept

36. What’s in an instruction? • An instruction tells the CPU • the operation to be performed via the OPCODE • where to find the operands (source and destination) • For a given instruction, the ISA specifies • what the OPCODE means (semantics) • how many operands are required and their types, sizes etc.(syntax) • Operand is either • register (integer, floating-point, PC) • a memory address • a constant