Editing IBM FDD Adapter

{{Infobox computer peripheral
| name          = IBM Floppy Disk Drive Adapter
| image         = [[File:IBM FDD Adapter card.jpg|260px]]
| caption       = IBM PC Original 5.25-inch Diskette Drive Adapter
| manufacturer  = IBM
| type          = 8-bit ISA floppy disk controller card
| release_date  = 1981 (with the original IBM PC)
| interface     = 8-bit ISA
| compatible    = [[IBM PC (5150)]], [[IBM PC XT (5160)]]
| connectivity  = 34-pin floppy ribbon header (supports two internal 5.25" drives)
}}

The '''IBM Floppy Disk Drive Adapter''' is the 8-bit ISA card that drives the 5.25" floppy disk drives in the [[IBM PC (5150)]] and [[IBM PC XT (5160)]]. The 5150 motherboard has no on-board floppy controller — every PC fitted with floppy drives includes this card, occupying one of the five ISA slots.

== Hardware ==

* '''NEC µPD765''' floppy disk controller (or the compatible Intel 8272A in some revisions).
* '''Supports up to two internal drives''' through the 34-pin ribbon header.
* '''Drives the [[Tandon TM100-1]], [[Tandon TM100-2|TM100-2]], TM100-2A''' and Micropolis-equivalent 5.25" drives at 250 kbit/s, MFM encoding.
* '''No BIOS expansion ROM''' — floppy support is built into the motherboard BIOS.

== Cable & Termination ==

The IBM FDD ribbon cable has a 7-wire twist between the two drive connectors. Drive 0 (A:) sits at the far end of the cable, beyond the twist; drive 1 (B:) is the middle connector. Both drives must be jumper-set to '''drive select 2''' — the cable twist remaps DS2 to DS0 on drive A. The drive at the end of the cable also requires its terminating resistor pack to be present; the middle drive must have the resistor pack removed.

== Common Faults ==

* '''POST 6xx error''' — the controller card itself. Reseat first.
* '''Drive light stuck on continuously''' — the ribbon cable is inserted backwards on either the card or the drive end.
* '''Both drives appear as drive A''' — termination resistor missing on the end drive, or the cable twist is wrong.

== References ==

* IBM, ''IBM 5150 Technical Reference'' (6025005, August 1981).

== Related Pages ==

* [[IBM PC (5150)]]
* [[Tandon TM100-1]]
* [[Tandon TM100-2]]
* [[IBM PC (5150) Troubleshooting Guide]]

[[Category:IBM]]