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Lecture 2.1

Lecture 2.1. Instructions: Introduction. Objectives. Understand that the instruction set is the repertoire of instructions of a computer Remember that the memory is always addressed at the unit of byte Memory only accepts byte addresses Convert between byte address and word address

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Lecture 2.1

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  1. Lecture 2.1 Instructions: Introduction

  2. Objectives • Understand that the instruction set is the repertoire of instructions of a computer • Remember that the memory is always addressed at the unit of byte • Memory only accepts byte addresses • Convert between byte address and word address • Tell the difference between big-endian computer and little-endian computer • Underline two key principles of machine design Chapter 2 — Instructions: Language of the Computer — 2

  3. Coverage • Textbook Chapters 2.1, 2.2, 2.3 Chapter 2 — Instructions: Language of the Computer — 3

  4. Instruction Set §2.1 Introduction • The repertoire of instructions of a computer • Different computers have different instruction sets • But with many aspects in common • Early computers had very simple instruction sets • Simplified implementation • Many modern computers also have simple instruction sets Chapter 2 — Instructions: Language of the Computer — 4

  5. The MIPS Instruction Set • Used as the example throughout the book • 32-bit Computer, i.e., MIPS-32 • Stanford MIPS commercialized by MIPS Technologies (www.mips.com) • Large share of embedded core market • Applications in consumer electronics, network/storage equipment, cameras, printers, … • One example of RISC instruction sets • Typical of many modern instruction set architectures (ISAs) • See MIPS Reference Data tear-out card, and Appendixes A and E Chapter 2 — Instructions: Language of the Computer — 5

  6. Representation of Memory Addresses • Memory addresses are given in the unit of byte Chapter 2 — Instructions: Language of the Computer — 6

  7. Save Words • A multiple-byte word is stored in multiple consecutive bytes • The address of a word matches the address of one of the multiple bytes within the word • Use the smallest address in general • In MIPS, words must start at addresses of multiples of 4 Chapter 2 — Instructions: Language of the Computer — 7

  8. Word Address for Convenience • Word address = Byte address ÷ 4 Chapter 2 — Instructions: Language of the Computer — 8

  9. Store words into memory Chapter 2 — Instructions: Language of the Computer — 9

  10. Two Key Principles of Machine Design • Instructions are represented as numbers and, as such, are indistinguishable from data • Programs are stored in alterable memory (that can be read or written to) just like data • Stored-program concept • Programs can be shipped as files of binary numbers • Computers can inherit ready-made software provided they are compatible with an existing ISA – leads industry to align around a small number of ISAs Chapter 2 — Instructions: Language of the Computer — 10

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