IBM FDD Adapter
| IBM Floppy Disk Drive Adapter | |
|---|---|
 |
|
| 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
[edit | edit source]- 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, 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
[edit | edit source]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
[edit | edit source]- 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
[edit | edit source]- IBM, IBM 5150 Technical Reference (6025005, August 1981).