Computer Architecture Chapter 2.8, Spring 2005 Department of - - PowerPoint PPT Presentation

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Computer Architecture Chapter 2.8, Spring 2005 Department of - - PowerPoint PPT Presentation

May 01, 2023 562 likes •685 views

Computer Architecture Chapter 2.8, Spring 2005 Department of Computer Science Kent State University 32-bit word alignment in byte addressed memory Aligned at 4 (Good): Unaligned at 5 ( Bad! ): 0 1 2 3 0 1

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SLIDE 1

Computer Architecture

Spring 2005 Department of Computer Science Kent State University

Chapter 2.8,

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SLIDE 2

32-bit word alignment in byte addressed memory

  • Aligned at 4 (Good):
  • Unaligned at 5 (Bad!):

4 8 MSB LSB 0 1 2 3 4 8 MSB 0 1 2 3 LSB

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SLIDE 3

Section 2.8: Communicating with People

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SLIDE 4

American Std Code for Info Interchange (ASCII): 8-bit bytes representing characters

| 124 l 108 L 76 < 60 , 44 FF 12 { 123 k 107 K 75 ; 59 + 43 11 z 122 j 106 J 74 : 58 * 42 LF 10 y 121 i 105 I 73 9 57 ) 41 tab 9 x 120 h 104 H 72 8 56 ( 40 bksp 8 w 119 g 103 G 71 7 55 ‘ 39 7 ACK EOT Null

Char

15 6 5 4 3 2 1

ASCII

v 118 f 102 F 70 6 54 & 38 u 117 e 101 E 69 5 53 % 37 DEL t s r q p

Char

127 116 115 114 113 112

ASCII

  • 111

O 79 ? 63 / 47 d 100 D 68 4 52 $ 36 c 99 C 67 3 51 # 35 b 98 B 66 2 50 “ 34 a 97 A 65 1 49 ! 33 ` 96 @ 64 48 space 32

Char ASCII Char ASCI I Char ASCII Char ASCII

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SLIDE 5

ASCII “Tricks”

  • “0” in ASCII -> encoded as 4810
  • -> 0011 00002
  • “6” in ASCII -> encoded as 5410
  • -> 0011 01102
  • “9” in ASCII -> encoded as 5710
  • -> 0011 10012
  • Unicode: all encodings for 0-127 are the same as ASCII. Why?
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SLIDE 6

More Data Transfer

  • Bytes (8-bit)
  • Load byte (lb)
  • Store byte (sb)
  • C++ signed char
  • Halfwords (16-bit)
  • Load halfword (lh)
  • Store halfword (sh)
  • C++ short
  • Load upper immediate (lui)
  • lui $t0, 255 What does $t0 hold after?
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SLIDE 7

More Data Transfer (2.9)

  • Load upper immediate (lui)
  • lui $t0, 255 What does $t0 hold after?

0000 0000 1111 1111 0000 0000 0000 0000 001111 00000 01000 0000 0000 1111 1111 Machine language instruction $T0 What is the value of this in hex? How about decimal (base 10)?

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SLIDE 8

Pseudoinstructions

  • Assembler supports some "instructions" that

are not implemented by the hardware

  • These are pseudoinstructions or synthetic

instructions

  • Makes assembly code easier to read/write
  • Assembler may use $at as a temporary

register

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SLIDE 9

Arithmetic

  • Absolute value
  • abs dest, src
  • Negate
  • neg dest, src
  • NOT
  • not dest, src
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SLIDE 10

Data Transfer

  • Load address
  • la dest, offset(base)
  • Load immediate
  • li dest, immed
  • Move register
  • move dest, src
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SLIDE 11

Branch

  • Branch if greater than or equal (bge)
  • bge src1, src2, target
  • Branch if greater than (bgt)
  • bgt src1, src2, target
  • Branch if less than or equal (ble)
  • ble src1, src2, target
  • Branch if less than (blt)
  • blt src1, src2, target