The computer is controlled by a controller , Arithmetic unit , storage , Input and output composition , The connection modes of various components are as follows :

Decentralized connection : Each part is connected separately

Bus connection : The components are connected to a set of public information transmission lines

The information transmission modes of the bus include : Serial and parallel

1. Bus structure computer

1.1 Single bus structure


IO Communication with main memory will not be affected CPU function ,CPU, Main memory ,IO Common single bus , fierce competition .

1.2 with CPU Dual bus structure with center


IO And main memory through the bus and CPU connect ,IO Communication with main memory will occupy PCU, So it will affect CPU efficiency .

1.3 Dual bus architecture centered on memory


CPU Use memory bus to communicate with main memory , Main memory and IO Communication uses system bus , No occupation CPU.

2. Bus classification

Different transmission modes : Parallel transmission bus , Serial transmission bus

Different connecting parts : On chip bus , system bus , Communication bus

On chip bus : Bus in chip

system bus : Information transmission line between computer components

        data bus : Transmit data information   Bidirectional transmission bus     Machine word length   Storage word length

        Address bus : Main memory location address or IO Device address     one-way   Storage address   IO address

        Control bus : Transmission control signal     one-way

Communication bus : Communication between computer systems or between computers and other systems

3. Bus characteristics


Bus characteristics :

1. mechanical properties   size   shape   Number of pins   Order of arrangement

2. Electrical characteristics   Transmission direction   Effective level range

3. Functional characteristics     Function of each transmission line   address   data   control

4. Time characteristics   Time sequence relationship of signals

4. Bus performance index

1. Bus width   Number of data lines

2. Standard transmission rate   Maximum number of bytes transferred per second MBps

3. Clock synchronization asynchronous     synchronization   Out of sync

4. Bus multiplexing     Address line and data line multiplexing

5. Number of signal lines     Address line , Sum of data and control lines

6. Bus control mode   Sudden   automatic   arbitration   logic   count

7. Other indicators   Load capacity

5. Bus standard

System and modules , A standard interface for interconnection between modules . The main standards are as follows :


The various standards are summarized as follows :


6. Bus structure

Single bus and multi bus

6.1. Single bus mode


The structure is simple , Easy to expand ;

The competition of system bus is fierce , Only one device is allowed to occupy the bus at the same time , The system efficiency is not high ;

6.2. Multi bus mode

Dual bus structure   Main memory through channel and IO signal communication   CPU efficient


6.3. Three bus structure       Main memory bus for CPU Communication with main memory    IO Bus for CPU And IO Equipment communication   DMA Bus for high speed IO Direct communication between device and main memory


6.4. Three bus structure 2      The local bus is used to connect CPU And Cache   Cache And main memory , The expansion bus is connected through the system bus   Main memory and IO Communication does not need to go through CPU


6.5. Four bus structure       


7. Example of bus structure

7.1 Bus structure of traditional Microcomputer

Low speed equipment , High speed equipment is connected with system bus through bus controller , Speed mismatch


7.2VL-BUS Local bus structure

Low speed equipment is connected with system bus through bus controller High speed equipment through VL-BUS The local bus is directly connected to the system bus

VL-BUS The bus speed will be limited CPU Performance of


7.3PCI Bus structure

utilize PCI The bridge makes the system bus and PCI Bus isolation , More flexibility


7.4PCI Multi layer bus structure


reference material :

Principles of Computer Organization -- Harbin Institute of Technology -- Liu Hongwei

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