Explain in detail the single bus structure?

Answer 1

In this type of inter-connection, the three units share a single bus. Hence the information can be transferred only between two units at a time. Here the I/O units use the same memory address space. This simplifies programming of I/O units as no special I/O instructions are needed. This is one of advantages of single bus organization.

Figure 3.5: Single-Bus Organization

The transfer of information over a bus cannot be done at a speed comparable to the operating speed of all the devices connected to the bus. Some electromechanical devices such as keyboards and printers are very slow whereas disks and tapes are considerably faster. Main memory and processors operate at electronic speeds. Since all the devices must communicate over the bus, it is necessary to smoothout the differences in timings among all the devices.

A common approach is to include buffer register with the devices to hold the information during transfers. To illustrate this let us take one example. Consider the transfer of an encoded character from the processor to a character printer where it is to be printed. The processor sends the character to the printer output register over the bus. Since buffer is an electronic register this transfer requires relatively little time. Now the printer starts printing. At this time bus and the processor are no longer needed and can be released for other activities. Buffer register is not available for other transfers until the process is completed. Thus buffer register smoothes out the timing differences between the processor, memory and I/O devices. This allows the processor to switch rapidly from one device to another interweaving its processing activity with data transfer involving several I/O devices.

Answer 2

A single bus architecture is a computing architecture in which all types of information are transported on the same electronic channel of communication. Modern computing has almost entirely shifted to multiple bus architectures.