MODULE11.pdf - MODULE 11 I\/O MANAGEMENT One of the important jobs of an Operating System is to manage various I\/O devices including mouse keyboards

MODULE11.pdf - MODULE 11 I/O MANAGEMENT One of the...

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MODULE 11: I/O MANAGEMENT
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FIGURE 11.1 11.2 Synchronous vs asynchronous I/O Synchronous I/O − In this scheme CPU execution waits while I/O proceeds Asynchronous I/O − I/O proceeds concurrently with CPU execution 11.3 Communication to I/O Devices The CPU must have a way to pass information to and from an I/O device. There are three approaches available to communicate with the CPU and Device. Special Instruction I/O Memory-mapped I/O Direct memory access (DMA) 11.3.1 Special Instruction I/O This uses CPU instructions that are specifically made for controlling I/O devices. These instructions typically allow data to be sent to an I/O device or read from an I/O device. 11.3.2 Memory-mapped I/O When using memory-mapped I/O, the same address space is shared by memory and I/O devices. The device is connected directly to certain main memory locations so that I/O device can transfer block of data to/from memory without going through CPU.
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FIGURE 11.2 While using memory mapped IO, OS allocates buffer in memory and informs I/O device to use that buffer to send data to the CPU. I/O device operates asynchronously with CPU, interrupts CPU when finished.
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