Floppy subsystem error: What is the most likely cause of an 'FDD controller failure' message after installing a floppy disk drive?

Introduction / Context:
Legacy floppy disk drives use a keyed ribbon cable with a twist designating drive A/B. Misorientation of the cable is a classic cause of boot-time controller errors and nonfunctional drive activity lights.

Given Data / Assumptions:

• Recent installation of a floppy drive precedes the error.
• Message indicates controller-level problem at POST.
• Hardware is otherwise functioning.

Concept / Approach:
Reversing the 34-pin cable at the drive or motherboard confuses the controller signals and power to the drive select logic, resulting in 'FDD controller failure' or constant LED illumination. This is more common than actual controller or drive defects. Correct orientation aligns pin 1 (marked by a stripe) on both ends with pin 1 headers.

Step-by-Step Solution:

Verification / Alternative check:
The drive LED stuck on at power-up strongly hints at a reversed cable. Correcting the orientation typically clears the fault instantly.

Why Other Options Are Wrong:
Floppy drives generally have no 'flash CMOS' requirement; CMOS flashing is unrelated. Jumper errors are rare on common 3.5-inch drives (cable twist selects A/B). Actual drive defects are less likely than a cabling mistake given the timing.

Common Pitfalls:
Forcing the connector on non-keyed headers; not recognizing pin 1 indicators on older boards.

Final Answer:
you installed the floppy disk drive cable backward