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Questions and Answers
Which of the following modes of IO operation involves the computer actively checking each device to see if it is ready for communication?
Which of the following modes of IO operation involves the computer actively checking each device to see if it is ready for communication?
What is the primary function of a device controller in IO management?
What is the primary function of a device controller in IO management?
Event Based I/O primarily requires processes to:
Event Based I/O primarily requires processes to:
Which IO device type typically operates with speeds of tens of bytes per second?
Which IO device type typically operates with speeds of tens of bytes per second?
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Which of the following mechanisms is NOT typically employed for asynchronous event communication in IO management?
Which of the following mechanisms is NOT typically employed for asynchronous event communication in IO management?
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What is the primary purpose of using Direct Memory Access (DMA)?
What is the primary purpose of using Direct Memory Access (DMA)?
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Which component is essential for executing Direct Memory Access transfers?
Which component is essential for executing Direct Memory Access transfers?
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In what way does cycle stealing by the DMA controller benefit system performance?
In what way does cycle stealing by the DMA controller benefit system performance?
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What context is stored to resume computation after an external interrupt?
What context is stored to resume computation after an external interrupt?
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What characterizes network-oriented traffic when processed in DMA mode?
What characterizes network-oriented traffic when processed in DMA mode?
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Study Notes
Introduction to I/O Management
- Interactions between humans and machines are facilitated by I/O devices such as printers and keyboards.
- Effective management of these devices directly impacts system throughput.
Communication Levels for I/O Devices
- I/O communication occurs at three levels: human input/output, device input/output, and computer network communication.
Device Speeds
- Character-oriented devices operate at tens of bytes per second.
- Block-oriented devices function significantly faster and cover a broader range.
- Communication occurs through data buses and device controllers.
Event-Based I/O
- Synchronization may be required for devices and processes to communicate.
- Processes can wait for signals indicating event occurrences.
- Operating systems use methods like polling, programmed data transfer, interrupts, and DMA.
Modes of I/O Operation
- Four basic modes are utilized:
- Polling: Sequentially checks device readiness.
- Programmed Mode: Communicates directly without CPU intervention.
- Interrupt Mode: Enables asynchronous processing.
- DMA Mode: Transfers data directly between devices and memory without CPU overhead.
Direct Memory Access (DMA)
- DMA facilitates large data transfers more efficiently than programmed I/O.
- Requires a DMA controller and involves specific command structures for operations.
- Cycle stealing optimizes CPU utilization by allowing batch data transfers.
Network-Oriented Traffic
- Network I/O often corresponds to component file transfers that can be managed using DMA.
- Traffic is typically bursty, requiring efficient communication strategies from the OS.
Interrupt Mode
- In interrupt mode, programs continue to execute until an I/O device raises an interrupt.
- This requires context storage to resume program execution after servicing the interrupt.
Types of Interrupts
- Categorized into:
- Internal Interrupts: Originating from memory processes or internal processor events.
- External Interrupts: Triggered by devices needing CPU attention.
- Software Interrupts: Occur from user programs calling system services.
Interrupt Servicing Steps
- When an interrupt is raised, the current program's state is saved, allowing resumed execution after processing the interrupt.
Identification of Interrupt Sources
- Using polling can slow down identification processes if many devices are present.
- Each interaction requires the kernel to resolve I/O commands through individual device drivers.
I/O and the Kernel
- The OS kernel coordinates I/O commands, establishing communication pathways between applications and hardware.
- Requests involve device identification, data provision, and efficient device management.
Buffer Management
- Buffers exist in main memory or caches to accommodate data transfer rate mismatches between devices and processors.
- Strategies for buffering include single, double, and circular buffers to manage data flow effectively.
Spooling in Printers
- Print requests from multiple users are queued (spooled) to prevent conflicts.
- The OS maintains a stable print queue accessible for monitoring.
Clocks and Time Management
- The CPU's system clock underpins time-related services for scheduling and resource tracking.
- Essential for real-time system operations and performance measurement.
Device Identification
- Operating systems assign exclusive addresses for devices, ensuring correct communication and operation management.
Caching Mechanisms
- Caches serve as fast intermediate storage, reducing latency between disk and memory or between CPU and memory.
- Improves data locality and overall performance, especially during disk rewrites.
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Description
Explore the critical aspects of Input Output management with emphasis on IO devices and their impact on system performance. This quiz covers issues in IO management and communication with various IO devices essential for efficient human-machine interaction.
