Device Management
Device drivers, interrupt handling, and DMA operations
Key Concepts
Device drivers, interrupts, DMA, I/O scheduling
Applications
Hardware abstraction, driver development, system optimization
Exam Focus
Device types, interrupt handling, DMA mechanisms
Device Types and Management
Hard Disk Drive Details
Characteristics
- • Sequential/Random Access
- • High Capacity
- • Non-volatile
Operations
- • Read
- • Write
- • Seek
- • Format
Device Driver Loading Simulation
Driver Status
Interrupt Handling
Hardware Interrupt
Source: I/O Devices
Priority: High
Handling: Immediate response required
- • Disk completion
- • Network packet arrival
- • Timer expiry
Software Interrupt
Source: System Calls
Priority: Medium
Handling: Scheduled processing
- • File operations
- • Memory allocation
- • Process creation
Exception
Source: CPU Events
Priority: Critical
Handling: Immediate exception handling
- • Division by zero
- • Page fault
- • Invalid instruction
Direct Memory Access (DMA)
DMA Process Steps
DMA Request
Device requests DMA controller for data transfer
Device signals DMA controller when ready for transfer
Bus Arbitration
DMA controller requests bus control from CPU
CPU grants bus control to DMA controller
Direct Transfer
Data transferred directly between device and memory
No CPU intervention during actual data transfer
Completion Interrupt
DMA controller signals transfer completion
CPU resumes normal operation and processes completion
DMA Advantages
- • CPU Efficiency: CPU free for other tasks during transfer
- • High Throughput: Direct memory access without CPU intervention
- • Reduced Overhead: Eliminates per-byte CPU involvement
- • Parallel Processing: Multiple operations can occur simultaneously
DMA Limitations
- • Hardware Cost: Requires additional DMA controller
- • Bus Conflicts: Competition for bus access
- • Cache Coherency: Potential cache consistency issues
- • Security Concerns: Direct memory access bypass
📝 Exam Tips
- • Understand different device types and their characteristics
- • Know interrupt handling mechanisms and priorities
- • Compare programmed I/O, interrupt-driven I/O, and DMA
- • Practice device driver architecture questions