Review of Principles of Computer Organization: An Overview of Computer Systems

1. Computer system overview

1.1 Hierarchy of computer systems

(1)
In terms of hardware, the computer system can be divided into five functional components:
arithmetic unit, controller, memory, input device, output device

It will be developed around its working principle, logic implementation, design method and the method of interconnection to form the whole machine

In a typical von Neumann machine, the conduction direction of data lines and control instructions is shown in the figure below: It

should be noted that the arithmetic unit and controller are integrated into the CPU, that is, only the memory and the CPU are left.

Regarding the functions of the five types of hardware:
Calculator: complete data temporary storage, transformation, arithmetic operation and logical operation functions
Controller: complete the command and control of the coordinated operation of various computer components, ensuring that instructions are executed in accordance with the predetermined order and steps
Memory : stores programs and data, and is the storage and exchange center for various information of computers. The memory can exchange information with the CPU and input and output devices.
Input devices: programs that input Yuan Shu data and process these data. The input information includes numbers, letters and control symbols, etc.
Output device: output the processing results of the computer. Output information includes alphanumeric tables and graphics

Features of von Neumann machines:

• The hardware is composed of arithmetic unit controller memory input and output devices
• Represent programs and data in binary code
• The working mode of stored program is adopted: the program and data are placed in the same memory in advance, and the program composed of instructions can be modified
• Instructions are stored in the memory according to the order of execution, and the instruction counter indicates the unit address of the instruction to be executed, which is generally incremented in order
• The machine is centered on the calculator, and the data transmission goes through the calculator
• The key idea of ​​von Neumann computer: store programs and execute them in address order

(2) Software
According to different object-oriented, it can be divided into system software and application software

• System software: system-oriented, used to manage the entire computer system, allocate system resources reasonably, and ensure the normal and efficient operation of the computer
• Application software: user-oriented, application program compiled according to the user's special requirements, this type of software usually realizes certain types of requirements of the user
  

1.2 Computer Performance Indicators

Basic word length: refers to the basic binary digits used to represent an operand or an instruction in a computer

• The basic word length is the data width that the CPU can process at one time, which is related to the adder, the number of bits in the register and the width of the internal data bus
• The word length marks the accuracy, the longer the word length, the higher the operation accuracy
• The word length affects the processing power and computing performance of the computer
• The word length is usually an integer multiple of bytes, such as 2, 4, 8, etc.
  

Computing speed: It reflects the speed of computer computing, and there are several different ways to measure the computing speed

• According to the frequency of different types of instructions in the calculation process, multiplied by different coefficients to obtain a statistical average, that is, the average operation speed
• Directly give the actual execution time of each instruction
  Note, take MIPS and MFLOPS as the unit of measurement to measure the operation speed

Several related concepts:
Response time (execution time): The time from the start of the event to the end of the event
Main frequency Fc: Each computer has a device that continuously generates fixed-frequency clock pulses, called the main clock. The frequency of the CPU main clock is usually called the main frequency of the machine, which is an important parameter to measure the speed of a computer.
CPU clock cycle: the reciprocal of the CPU main frequency Tc
CPI (Cycle Per Instruction): the average number of clock cycles required to execute an instruction
CPU execution time: (the total time is equal to the total number of instructions in the program In the number of clock cycles required to execute an instruction CPI CPU time period Tc)

$$MIPS=\frac{I_N}{T_{CPU}\ast 10^6}=\frac{I_N}{I_N\ast CPI\ast T_C\ast 10^6}=\frac{F_C}{CPI\ast 10^6}$$

Other solutions to the third question:
In order to get the number of clock cycles required for each instruction, you can divide the execution time of each instruction by the cycle length of the machine, as in the title; you
can also use the number of cycles in one second divided by 8M Number of instructions that can be processed per second 0.4 MIPS

It should be noted that in the fourth question, it is mentioned that
if the on-chip logic circuits of the machine are the same, the CPI (the number of clock cycles required for each instruction is the same, that is, the difference between different machines lies in the CPU frequency)