【Computer composition principle】Introduction to computer system

Introduction to Computer System

1. Basic knowledge

(1) Classification of computers

Electronic computers are generally divided into two categories: electronic analog computers and electronic digital computers.

	Electronic digital computer	Electronic analog computer
Data representation	Numbers 0 and 1	Voltage
Calculation	Digital counting	Voltage combination and measured value
control method	Program control	On-disk connection
accuracy	high	bottom
Data storage	Big	small
Logical judgment	Strong	no

• Electronic analog computer

  "Analog" means a similar meaning. For example, a slide rule uses length to indicate the number of clocks, and a pointer rotates on the dial to indicate time; an electric meter uses an angle to reflect the amount of electricity. These are the characteristics of analog computing devices and analog computers. The value is represented by a continuous quantity, and the symbol operation process is also continuous.

• Electronic digital computer

  The electronic digital computer is developed on the basis of the abacus. It uses numbers to express the size of the quantity. The main feature of the digital computer is the bitwise operation and the calculation is discontinuous.

  The definition of electronic digital computer progress can be divided into chip computers and general-purpose computers. Special and general-purpose computers are divided according to the efficiency, speed, price, economic efficiency and adaptability of the computer.

  • Dedicated computer

    A dedicated computer is the most effective, economical and fastest computer, but its adaptability is poor.

  • General purpose computer

    General-purpose computers are highly adaptable, but at the expense of efficiency, speed, and economy.

    General-purpose computers can be divided into supercomputers, mainframes, servers, PCs, single-chip computers, and multi-core computers. Their difference lies in size, simplicity, power loss, performance indicators, data storage capacity, command system scale and machine price.
    

(2) The development of computers

• A brief history of the development of computers
  

• The development trend of computers

  • miniaturization
  • Networked
  • Mega
  • Intelligent

(3) Computer performance indicators

• Throughput

  • The amount of information that can be processed in a certain time interval

• Response time

  • A measure of the time between when the input is valid and when the system responds

• Utilization rate

  • The percentage of time the system is actually used in a given time interval

• Processor word length

  • The number of bits that the arithmetic unit can complete binary operations at a time

• Bus width

  • The number of internal bus bits for interconnection between arithmetic unit and memory

• Memory capacity

  • The total number of all storage units of the memory

• Memory bandwidth

  • The amount of binary number information read from the memory per unit time

• Main frequency/clock cycle

  • The frequency of the main clock is called the CPU main frequency, and the reciprocal of the main frequency is the cycle

• CPU execution time

  • CPU time used to execute general programs

  • CPU execution time = number of CPU clock cycles × CPU clock cycles

• CPI

  • Cycle Per Instruction The number of cycles per instruction, that is, the average number of clock cycles required to execute an instruction

  • CPI = the number of CPU clock cycles required to execute a certain program ÷ the number of instructions contained in the program

• MIPS

  • Million Instructions Per Second How many million fixed-point instructions are executed per second

  • MIPS=number of instructions÷(program execution time×1 $0^6$）

• FLOPS

  • floating-point operations per second

  • FLOPS = the number of floating point operations in the program ÷ program execution time (s)

2. Introduction to Computer System

(1) Hardware system

①Hardware system composition

• Central Processing Unit CPU

  • Controller
  • Arithmetic unit

• Bus system

  • Bus and input and output interface

• I/O device

  • input device
  • Output device

• Memory

  • cache
  • Main memory
  • Virtual storage (disk device)

②Introduction to main hardware

• Operator
  primary function arithmetic is addition, subtraction, multiplication, and the like in addition to the arithmetic operation. In addition, logic operations can also be performed, so it is often called ALU (arithmetic logic operation unit).
  • Use binary numbers (easy to implement)
  • The more digits, the higher the calculation accuracy
• Memory
  saves or "memorizes" the original data and the steps of solving the problem, and it stores the binary code represented by 0 or 1
  • The main memory uses semiconductor devices as memory, and a semiconductor flip-flop stores a binary bit
  • Storage unit : Store n flip-flops with an n-bit binary number in the memory to form a storage unit
  • Memory address : The memory is composed of many storage units, and the number of each storage unit is called the address
  • Storage capacity : the total number of all storage units in the memory. Usually expressed in units of "KB, MB, GB, TB", etc.
  • Divided into: internal memory (main memory) and external memory (auxiliary memory)
• The controller
  controls the computer's various components to work
  in an orderly manner: according to the instruction sequence arranged by the calculation program, first fetch an instruction from the memory and put it in the controller, the operation code of the instruction is analyzed and judged by the decoder, and then according to the instruction Nature, execute this instruction, and perform the corresponding operation. Then fetch the second instruction from the memory, execute the second instruction, and so on
  • The instruction has two parts: the nature of the operation ( opcode ) and the address of the operation ( address code )
  • The period of instruction fetching is called the instruction fetch cycle
  • The period of execution of the instruction is called the execution cycle
  • The time to fetch the instruction and execute the completed instruction is called the instruction cycle
• Adapters and input and output devices
  • The input device converts a certain form of information that people are familiar with into a form of binary information that can be received and recognized inside the machine
  • The output device transforms the result of computer processing into a form of information that can be received and recognized by humans or other machines
  • I / O devices through often referred to as peripheral devices
  • The adapter (I/O interface) is equivalent to a converter, which can ensure that the peripheral device sends or receives information in the form required by the computer
• System bus The
  system bus constitutes the skeleton of the computer system and is a common channel for data transmission between multiple system components

(2) Software system

(3) The hierarchical structure of the computer system

• Hierarchical structure of computer system
  
• Software and hardware interface
  

3. The design idea of ​​electronic computer-storage program, program control

(1) Store program, program control

• Stored procedure

  Store the problem-solving program (instruction sequence) in the memory

• Program control

  The controller controls the whole computer to complete the calculation tasks in a coordinated manner according to the stored program

(2) The basic idea of ​​von Neumann computer

• Represents data and instructions in binary form. The instruction is composed of opcode and address code
• The program and data are stored in the memory, so that the computer takes out instructions from the memory and executes them when it is working, and automatically completes the calculation task. This is the "stored program" and "program control"
• The execution of instructions is sequential, that is, they are generally executed in the order in which the instructions are stored in the memory, and the program branch is implemented by the transfer instruction
• The computer is composed of five basic components: memory, arithmetic unit, controller, input and output equipment

(3) Instruction flow and data flow

• If a word is an instruction, it is called instruction word
• A word represents the data to be processed, called a data word
• The information read from the memory in the instruction fetch cycle is the instruction stream, which flows to the controller,
  while the information read from the memory in the execution cycle is the data stream, which flows from the memory to the arithmetic unit.
• In terms of time: in the fetch cycle, the information read by the CPU from the memory must be instructions; and the information read or written from the memory during the execution cycle must be data.
• Spatially: instructions must flow to the controller; and data flow between the memory (or registers) and the arithmetic unit