28. Lecture – 35
DMA (Direct Memory Access) transfer allows hardware devices to transfer data directly to and from memory without involving the CPU, thereby freeing up the processor for other tasks. This chapter discusses the need for DMA, its operational principles, and how it alleviates processor workload compared to programmed and interrupt-driven I/O. Additionally, it covers design considerations for effective DMA controller implementation.
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What we have learnt
- DMA transfers data between I/O devices and memory without processor intervention.
- Using DMA can significantly improve system performance by allowing the CPU to perform other tasks during data transfer.
- The design of a DMA controller is crucial for effective data management between devices and memory.
Key Concepts
- -- Direct Memory Access (DMA)
- A method that allows devices to directly transfer data to and from memory without CPU involvement, improving efficiency.
- -- DMA Controller
- A hardware component that manages DMA transfers, effectively handling data exchanges between devices and memory.
- -- I/O Module
- A component that facilitates communication between the processor and external devices, providing an interface for data exchange.
- -- Programmed I/O
- An I/O transfer method where the CPU actively manages data transfers through repeated checks on device status, resulting in CPU overhead.
- -- InterruptDriven I/O
- An I/O transfer mechanism where devices send interrupts to the CPU, requiring context switching and temporarily halting the CPU's current tasks.
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