What is the primary benefit of Direct Memory Access (DMA) in I/O operations?

• A. Direct Memory Access allows devices to transfer data to/from memory with little CPU involvement.
• B. DMA increases CPU overhead.
• C. DMA stores data permanently on disk.
• D. DMA manages virtual memory translations.

Answer: (A)

The main idea is that DMA lets a peripheral move data directly to or from system memory with minimal CPU involvement. Once the CPU sets up the transfer by providing the memory address, the number of bytes, and the direction, the DMA controller takes over the data movement across the system bus. It handles the address generation, handshaking with the device, and the actual byte transfers, then signals completion (often with an interrupt) so the CPU can continue with other work. This offloads the repetitive, byte-by-byte copying from the CPU, increasing throughput for I/O-heavy operations.

This isn’t about storing data on disk or translating virtual to physical memory, which are separate responsibilities handled by storage subsystems and the memory management unit, respectively. It also isn’t about increasing CPU overhead; it’s specifically intended to reduce it by handling transfers autonomously.