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cop4600-sp08-quiz4Solutions - of the I/O 2(2.5 pts Draw a...

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COP4600 Operating Systems Solutions for Quiz 4 Prepared by Tuba Yavuz-Kahveci University of Florida [email protected] Questions There are two questions. Please read the questions carefully. Good luck! 1. (2.5 pts) Describe Interrupt-driven I/O and I/O using Direct Memory Access (DMA). Answer: (a) Interrupt-driven I/O : I/O for n-unit data requires n requests to the de- vice controller and n interrupts are generated on the CPU by the device controller to notify the completion of the individual requests. (b) I/O using DMA : I/O for n-unit data requires 1 request to the DMA controller, which in return programs the device controller and 1 interrupt is generated by the DMA controller on the CPU to notify the completion
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Unformatted text preview: of the I/O. 2. (2.5 pts) Draw a Fgure to describe the layers of the I/O software and explain what each layer does. Answer: ±rom bottom to up: (a) Interrupt handler: Saves the state of the current process, processes in-terrupts generated by the devices by calling the appropriate interrupt handling procedure, and calls the scheduler. (b) Device driver: Programs the device controller by writing to its control and data registers to do I/O and to conFgure the device. (c) Device independent software: Provides protection, error reporting, bu²er-ing, etc. (d) User-level I/O software: Provides spooling, formatting, etc....
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