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Computer Bus Structure

Updated on November 17, 2010

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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    • profile image

      milind 6 years ago

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

    • profile image

      Ashutosh Kumar 5 years ago

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

    • profile image

      ravi 5 years ago

      excellent

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      fathima 5 years ago

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

    • profile image

      Pradeep kumar 5 years ago

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

    • profile image

      anees 5 years ago

      superb

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      it is easy to understand nice

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      superb explanation.

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      gud one

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      nice one

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      very useful

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      ..yeah

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      cath 5 years ago

      nice!now i understand..:)

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      nice!now i understand..:)

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      Rejie 5 years ago

      it is very useful for students like me, thanks! ^_^

    • profile image

      saranya 5 years ago

      easy to understand

      this force me to learn more.

    • profile image

      PAUL NEWMAN 5 years ago

      good explanation....

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      awesome matter

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      Excellent,explaind in simple words.Nyc.

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      excellent

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      ultimate 1

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      nice!

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      It is very useful and easy to understand

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      very easy to understand and very helpful to me.thanks a lot.

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      Ali Hakim 4 years ago

      goog

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      it s very easy to understand

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      well...is very easy!

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      simply to understand

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      well understood

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      good

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      good

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      it's very easy

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      it's very easy to understand

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      all right guys i am happy to atten my test without having refernce books by having this notes

    • profile image

      anju 4 years ago

      thnks :)

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      temesgen oljera 3 years ago

      thank u

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      amala 3 years ago

      thanks

    • profile image

      Anu 3 years ago

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

      http://www.elec-trix.blogspot.in/2013/10/bus-struc...

    • profile image

      nita bhandekar 3 years ago

      it is very easy notes

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