Devices and DMA Usage on Legacy PCs Among the following peripherals, which one is well known for using a DMA (Direct Memory Access) channel in ISA-era PCs?

Introduction / Context:
Direct Memory Access (DMA) allows devices to transfer data to or from system memory with minimal CPU intervention. Understanding which legacy peripherals commonly used DMA helps troubleshoot resource conflicts and configuration issues on older systems.

Given Data / Assumptions:

• Classic ISA sound cards (e.g., Sound Blaster family) needed DMA for digitized audio capture/playback.
• Many modems and NICs relied on programmed I/O or bus mastering rather than fixed ISA DMA channels.
• We are considering typical, exam-oriented defaults for legacy hardware.

Concept / Approach:

ISA sound cards commonly used DMA channels (e.g., DMA 1 and 5) to stream audio with low CPU overhead. While some advanced NICs used bus mastering (a form of DMA), they did not typically reserve ISA DMA channels in the same way. Modems generally operated via the UART/serial interface without needing an ISA DMA assignment.

Step-by-Step Solution:

Verification / Alternative check:

Driver setup for ISA sound cards typically asks for IRQ and DMA channel selections; NICs and modems rarely do for ISA DMA channels.

Why Other Options Are Wrong:

“All of the above” overgeneralizes; modems and many NICs do not require ISA DMA channels. “None of the above” ignores the well-known DMA use by sound cards.

Common Pitfalls:

Confusing bus mastering with ISA DMA channel assignments, or assuming any high-throughput device must use DMA in the ISA sense.

Final Answer:

Sound Card