Standard PC IRQ Usage IRQ6 is typically reserved for which hardware device in classic PC architectures?

Introduction / Context:
Interrupt Request Lines (IRQs) are used by devices to signal the CPU. Classic PC platforms assign standard IRQs to common peripherals, and knowing these defaults speeds up troubleshooting legacy hardware and embedded systems derived from PC designs.

Given Data / Assumptions:

• Standard ISA-derived IRQ mapping.
• Legacy floppy disk controller present.
• PS/2 keyboard and serial/parallel devices use their traditional IRQs.

Concept / Approach:

In the classic mapping, IRQ6 is used by the floppy disk controller. This convention persists in many BIOS and service references. The keyboard controller uses IRQ1, typical parallel ports use IRQ5 or IRQ7, and modems often share IRQ3 or IRQ4 depending on COM port assignment.

Step-by-Step Solution:

Verification / Alternative check:

BIOS setup screens and service manuals list IRQ6 for the floppy controller. OS device managers from DOS/Windows era corroborate this default routing.

Why Other Options Are Wrong:

Keyboard controller: IRQ1 by default. LPT2: Commonly IRQ5 or IRQ7. Modem: Typically IRQ3 or IRQ4 associated with COM2/COM1, not IRQ6. None of the above: Incorrect because floppy is correct.

Common Pitfalls:

Assuming PnP/ACPI modern systems always follow ISA defaults; while abstracted today, historical mappings still appear in exam and repair contexts.

Final Answer:

The floppy