Which one suited, polling/interrupt, for the following types of system? Give reason. a) A system dedicated to controlling single I/O devices. b) A work station running as heavily used web server.



A system dedicated to controlling single I/O devices:
Polling is suited for the system dedicated to controlling single I/O device. The host repeatedly checks the busy bit on the device until it becomes clear. Polling can be very fast and efficient, if both the device and the controller are fast and if there is significant data to transfer. It becomes inefficient, however, if the host must wait a long time in the busy loop waiting for the device, or if frequent checks need to be made for data that is infrequently there.
A work station running as heavily used web server:
Interrupt is suited for workstation running as heavily used web server. Interrupts allow devices to notify the CPU when they have data to transfer or when an operation is complete, allowing the CPU to perform other duties when no I/O transfers need its immediate attention. The CPU has an interrupt-request line that is sensed after every instruction. The interrupt handler determines the cause of the interrupt, performs the necessary processing, performs a state restore, and executes a return from interrupt instruction to return control to the CPU.

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