2 Computer Organization, Bus Structure A communication pathway connecting two or more devicesWhen a word of data is transferred between units all its bits are transferred in parallelie. The bits are transferred simultaneously over many lines, one bit per line.A group of lines that serves as a connecting path for several devices is called a busA group of lines connected to different devices is called bus. Bus can carry data and control signals Single bus – simple way to interconnect functional units.popo
3 Computer Organization, Bus Structure Single Bus Structurepopo
4 Computer Organization, Bus Structure All units are connected to this busBus can used only for one transfer at a timeSo only 2 units can actively use the bus at any given time.Only one device at a time can successfully transmit.Single bus – low cost and It is flexible for attaching diff devicesBy using multiple bus simultaneously can transfer more than one data at a timeThis leads to increase the performance of the system.So the bus can carry several data at a time in parallel such asPowerInstructionsDataAddressesCommandspopo
5 Computer Organization, Bus Structure Multiple-Bus OrganizationThe following Figure shows a three-bus structure.All registers are combined into a single block called register file with three ports: 2 outputs allowing 2 registers to be accessed simultaneously.Buses A and B are used to transfer source operands to the A and B inputs of ALU, and result transferred to destination over bus C.popo
7 Computer Organization, Bus Structure Diff units in a system having diff speedKeyboardPrinter are relatively slowsome units are very fast all these devices communicate with each other over the same busin order to communicate all types of units smoothly include buffer registers with the devices to hold the data during transfer. eg transfer of data between processor and printerProcessor sent data over the bus to printer bufferOnce the buffer is loaded the printer can start printing With out the interaction of the processorThe bus and processor are now free to do another work.popo
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