for a comp to archieve its operation, the functionnal units need to communicate with eah other.They need to be connected
group of parallel wires used to connect the functional units is called a bus
Each bus can transfer one bit of data
no of wire = len(word)
bus: connecting path for several devices
there is data bus, addr bus, control bus,etc
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if it was a single bus structure all units are connected to a bus so only one transfer at a time,only 2 device can communicate at a time
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single bus is the simplest form of a abus
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multiple buseds have concurrency in operation better performation but expensive
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-Drawbacks
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The devices connectted to a bus vary widely in their speed of operation
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devices relatively slow (printer, keyboard)
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fast(optical disc)
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faster(memory, processor)
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to cope with it:
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a common approach is to include buffer regisrers with the device to hold the info during transfers
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two-bus sructure/multiple-bus structures
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the main virtue for using single bus structure is - cost effective
multiple buses and buffer registers - are used to overcome diff in data transfer speeds of various devices