System Programming

NTNU 系統程式

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Back to System Programming

tags: SystemProgramming 110-1 CSIE 選修 NTNU

Ch.01 Background

1.1 Introduction

• Definition
  • 由支持計算機操作的各種程式組成

1.2 System Software and Machine Architecture

1.3 The Simplified Instructional Computer (SIC)

• Simplified Instructional Computer(SIC)
  • Comes in two versions
    • The Standard model
    • An XE version(extra equipments, extra expensive)
  • The two versions has been designed to be upward compatible

1.3.1 SIC Machine Architecture

• Memory
  • consists of 8-bits bytes
  • word: 3 consecutive bytes(24 bits)
  • total: 2¹⁵ bytes
• Registers
  • 5 registers
    • 24 bits length (each)

      Mnemonic	Number	Special use
      A	0	Accumulator
      X	1	Index register
      L	2	Linkage register
      PC	8	Program counter
      SW	9	Status word

• Data Formats
  • Integers are stored as 24-bit binary number
  • 2’s complement representation for negative values
  • Characters are stored using 8-bit ASCII codes(at right most bits)
  • No floating-point hardware on the standard version of SIC
• Instruction Formats
  • Standard version of SIC
  • 24 bits

    opcode	x	address
    8	1	15

  The flag bit
  $x$ is used to indicate indexed-addressing mode
• Buses
  • Data Bus: 24/8 bits
  • Address Bus: 15 bits
• Addressing Modes
  • There are two addressing modes available, indicated by x bit in the instruction

    Mode	Indication	Target Address calculation
    Direct	x=0	TA=address
    Indexed	x=1	TA=address=( $X$)

  (
  $X$): the contents if register
  $X$

1.3.2 SIC/XE Machine Architecture

• Memory
  • Maximum memory available on a SIC/XE system is 1 megabyte(
    $2^{20}$bytes)
• Instruction format
  • Format 1(1 bytes)

    op
    8

    • Ex.

      Mneminic	Format	Opcode	Effect
      FIX	1	C4	A <- (F)[convert to integer]

  • Format 2(2 bytes)

    op	r1	r2
    8	4	4

  Format 1 & 2 are instructions that do not reference memory at all.

  • Format 3(3 bytes)

    op	n	i	x	b	p	e	disp
    6	1	1	1	1	1	1	12

  • Format 4(4 bytes)

    op	n	i	x	b	p	e	address
    6	1	1	1	1	1	1	20

  • Addressing mode for format 3

    Mode	Indication	Target address calculation	Notes
    Base relative	b=1, p=0	TA=(B)+disp ( $0\le disp\le 4095$)
    Program-counter relative	b=0, p=1	TA=(PC)+disp ( $-2048\le disp\le 2047$)	指令跟指令的間隔通常小於 $2^{12}$

• Registers
  • Additional registers are provided by SIC/XE

    Mnemonic	Number	Special Use
    B	3	Base register
    S	4	General working register
    T	5	General working register
    F	6	Floating point accumulator(48 bits)

• 48-bit floating-point data type (他說不重要)
• Instruction Format
  • 15 bits in SIC
  • 20 bits in SIC/XE

About n, i, x, b, p, e !

• Target address

  n, i: how to use the target address(TA)

  n	i
  1	1	Direct(Simple) addressing
  1	0	Indirect addressing (尋寶遊戲)
  0	1	Immediate addressing (no memory access)
  0	0	相容 SIC

• e

  e	Format
  0	format 3
  1	format 4

• About TA 計算

  Mode	Indication	Target address calculation	Notes
  Base relative mode	b=1, p=0	TA=(B)+disp+(X) ( $0\le disp\le 4095$)
  Program-counter relative mode	b=0, p=1	TA=(PC)+disp+(X) ( $-2048\le disp\le 2047$)	指令跟指令的間隔通常小於 $2^{12}$

SIC Programming Examples

    LDA    ZERO
    STA    INDEX

x = a + b * c
y = x * a

LDA b
MUL c
ADD a
STA x
LDA x
MUL a
STA y

1 4 Traditional (CISC) Machines

1.5 RISC Machines