PC Hardware Resources: Which Expansion Device Uses a DMA Channel? Identify the component that typically relies on DMA (Direct Memory Access) for high-throughput, low-CPU-overhead data transfers.

Introduction / Context:
Legacy PC architectures (ISA/early PCI era) assigned hardware resources such as IRQs, I/O ports, and DMA channels to devices. Understanding which peripherals actually used DMA helps with troubleshooting conflicts and performance issues in older systems and embedded PCs.

Given Data / Assumptions:

• Context is classic PC hardware (ISA/early PCI) rather than purely modern bus-mastering NICs.
• DMA provides memory transfers without CPU copying.
• We evaluate which listed device class is most characteristically associated with DMA usage.

Concept / Approach:

ISA sound cards (e.g., Sound Blaster family) commonly used DMA channels (such as DMA 1 or 5) to stream digitized audio to and from memory with minimal CPU intervention. While some network cards later used bus mastering (a DMA-like concept), the quintessential and widely taught example of DMA usage in A+ and legacy curricula is the sound card.

Step-by-Step Solution:

Verification / Alternative check:

Check classic configuration utilities (DIAGNOSE/CTCU) and manuals listing DMA assignments for audio playback/record. Lab configuration of DOS games also required setting IRQ/DMA for sound cards.

Why Other Options Are Wrong:

Modems: interrupt-driven serial I/O, not DMA. Network cards: while some can DMA via bus mastering, the expected exam answer emphasizes the sound card's historical, explicit DMA channel usage. “All of the above” overgeneralizes.

Common Pitfalls:

Confusing PCI bus mastering with legacy ISA DMA channels, or assuming every high-speed device necessarily used a classic DMA channel.

Final Answer:

Sound Card