Computer Bus Structure

Bus Structure

A bus is a collection of wires that connect several devices within a computer system. When a word of data is transferred between units, all its bits are transferred in parallel. A computer must have some lines for addressing and control purposes.

Three main groupings of lines:

1. Data Bus. This is for the transmission of data.

2. Address Bus. This specifies the location of data in MM.

Control Bus. This indicates the direction of data transfer and coordinates the timing of events during the transfer.

Single Bus Structure

All units are connected to a single bus, so it provides the sole means of interconnection. Single bus structure has advantages of simplicity and low cost.

Single bus structure has disadvantages of limited speed since usually only two units can participate in a data transfer at any one time. This means that an arbitration system is required and that units will be forced to wait.

Only two units can actively use the bus at any given time. Bus control lines are used to arbitrate multiple requests for the use of the bus.

Buffer Registers are used to hold information during transfers.

Two Bus Structure

In the first configuration, the processor is placed between the I/O unit and the memory unit. The processor is responsible for any data transfer between the I/O unit and the memory unit. The processor acts as a “messenger.” In this structure, the processor performance and capability is not being maximized. Most of the time, the processor is doing data transfer between these units instead of performing more complex applications. Also, the processor is idle most of the time waiting for these slow devices.

In the second configuration, I/O transfers are made directly to or from the memory. A special purpose processor called peripheral processor or I/O channel is needed as part of the I/O equipment to control and facilitate such transfers. This special processor is the direct memory access(DMA) controller. It allows main memory to perform data transfer between I/O units.

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Comments 63 comments

milind 6 years ago

what if we make uch a line that function as both address ine controll line data line

Ashutosh Kumar 5 years ago

very usefull,, if possible make it more detailed.... thnx.

ravi 5 years ago


fathima 5 years ago

it is usefull to us... & it's easy to understand...

Pradeep kumar 5 years ago

Ya fine.. Its very easy to understand.. Very simple defi n explainations..

anees 5 years ago


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karthik 5 years ago

very useful

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cath 5 years ago

nice!now i understand..:)

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Rejie 5 years ago

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PAUL NEWMAN 5 years ago

good explanation....

tanvi 5 years ago

awesome matter

Sameer 4 years ago

Excellent,explaind in simple words.Nyc.

sandy 4 years ago

It is very easy to understand....thanks.

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ultimate 1

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Priya 4 years ago

It is very useful and easy to understand

khyati 4 years ago

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Ali Hakim 4 years ago


vicky 4 years ago

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ravi 4 years ago

it s very easy to understand

sssh 4 years ago very easy!

mallemkondaiah 4 years ago

simply to understand

A.kanyakumari 4 years ago

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cheza akoo 4 years ago

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Menchu 4 years ago

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anjit 4 years ago

nice and fantastic

jazmine 4 years ago

its very useful!

shosha 4 years ago

thanks 4 the information it's very useful

seth 4 years ago

well understood

laxma reddy 4 years ago


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deepak singh 4 years ago

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Sathish 4 years ago

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sweety 4 years ago

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anju 3 years ago

thnks :)

temesgen oljera 3 years ago

thank u

amala 3 years ago


Anu 3 years ago

for more info regarding bus structures........

nita bhandekar 3 years ago

it is very easy notes

lokesh8gmail.comm 3 years ago

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micky 3 years ago

awesome.... short sweet and simple

mick 2 years ago


Mang Kanor 2 years ago

Thank you for the information , IT will help me for my Research

Prince Hari 21 months ago


susmita 5 months ago

vry nice

Aswini adumbil 3 months ago

Very nice

Aswini adumbil 3 months ago

Very nice

evans 6 weeks ago


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