PS/2 Floppy Drive Interface Pinouts

40-Pin Card-Edge Interface
34-pin Header Interface
Enhanced 34-pin Header Interface (Media Sense)
40-pin Planar Interface (8555)
40-pin Planar Interface (Media-Sense) (95 XP)
44-pin Planar Interface (Media-Sense) (95A, Lacuna, 85 K/N)

Content created by Tomáš Slavotínek and Louis Ohland. Sources linked down below.


PS/2 Floppy Drive Connectors

Signals and voltages are transferred between the system board and the diskette drives by a cable or printed circuit board. The printed-circuit board provides a 2- by 20-pin card edge connector for each diskette drive, with a locator key between pins 34 and 36. The cable interface provides a 2 x 17-pin header connector to each diskette drive, with a locator key below pin 17. The following tables show the signals and DC voltages for each diskette drive connector type.

Extracted from PS/2 3.5-inch Diskette Drives Technical Reference (S42G-2194-00), 2nd Ed., Oct 1992, pages 10-12. (Unless noted otherwise.)

Note: There are differences between the 1990 Tech Ref and the '92 Tech Ref Signal names for the Enhanced 34-pin interface. See the Notes below the table. I believe the additional definition is related to the floppy controller used for the EE floppies.


40-Pin Card-Edge Interface

PinSignalPinSignal
1Ground2-High Density Select
3Reserved4Reserved
5Ground6Reserved
7Ground8-Index
9Ground10Reserved
11Ground12-Drive Select
13Ground14Reserved
15Ground16-Motor Enable
17Ground18-Direction In
19Ground20-Step
21Ground22-Write Data
23Ground24-Write Enable
25Ground26-Track 0
27Ground26-Write Protect
29Ground30-Read Data
31Ground32-Head 1 Select
33Ground34-Diskette Change
35Ground36Ground
37Ground36+5 Vdc
39Ground40+12 Vdc


34-pin Header Interface

This connector is for drives and controllers that do not support media sense.

PinSignalPinSignal
1Ground2-High Density Select
3+5 Vdc4Drive Type ID 1
5Ground6+12 Vdc
7Ground8-Index
9Ground10Reserved
11Ground12-Drive Select
13Ground14Reserved
15Ground16-Motor Enable
17Ground18-Direction In
19Ground20-Step
21Ground22-Write Data
23Ground24-Write Enable
25Ground26-Track 0
27Ground28-Write Protect
29Ground30-Read Data
31Ground32-Head 1 Select
33Ground34-Diskette Change


Enhanced 34-pin Header Interface (Media Sense)

This connector is for drives and controllers that support media sense.

PinSignalPinSignal
1Ground2Data rate Select 1
3+5 Vdc4Drive Type ID1/Drive status 1
5Ground6+12 Vdc
7Ground8-Index
9Drive Type ID0/Drive status 010Reserved
11Ground12-Drive Select
13Ground14-Security Command *
15Ground16-Motor Enable
17Media Type ID1/Drive status 318-Direction In
19Ground20-Step
21Ground22-Write Data
23Ground24-Write Enable
25Ground26-Track 0
27Media Type ID0/Drive status 228-Write Protect
29Ground30-Read Data
31Ground32-Head 1 Select
33Data rate Select 034-Diskette Change

All blue text is not present in '90 Tech. Ref.
* Not supported by all drives or all systems. '90 Tech. Ref. has this Reserved.


40-pin Planar Diskette Interface (8555)

PinSignalPinSignal
1Reserved2-High Density Select
3+5 Vdc4Reserved
5Ground6+12 Vdc
7Ground8-Index
9Ground10Reserved
11Ground12-Drive Select
13Ground14Reserved
15Ground16-Motor Enable
17Ground18-Direction
19Ground20-Step
21Ground22-Write Data
23Ground24-Write Enable
25Ground26-Track 0
27Ground28-Write Protect
29Ground30-Read Data
31Ground32-Head 1 Select
33Ground34-Diskette Change
35Ground36Ground
37Reserved38+5 Vdc
39Ground40+ 12 Vdc

Information extracted from IBM PS/2 Model 55 SX Technical Reference, Type 9595, page 2-8, Figure 3-5.


40-pin Planar Diskette Interface (Media-Sense)

This connector is found on the 90 XP and 95 XP planars.

PinSignalPinSignal
1-2nd Drive installed [D0 & D1 pin 1]2Data rate Select 1
3+5 Vdc4Drive Type ID1
5Ground6+12 Vdc
7Ground8-Index
9Drive Type ID010-Motor Enable 1 [D0 pin 16]
11Ground12-Drive Select 0 [D1 pin 12]
13Ground14-Drive Select 1 [D0 pin 12]
15Ground16-Motor Enable 0 [D1 pin 16]
17Media Type ID118-Direction In
19Ground20-Step
21Ground22-Write Data
23Ground24-Write Enable
25Ground26-Track 0
27Media Type ID028-Write Protect
29Ground30-Read Data
31Ground32-Head 1 Select
33Data rate Select 034-Diskette Change
35Ground36Drive Select 2 [D2 pin 12]
37Ground38Ground
39Ground40-Motor Enable 2 [D2 pin 16]

Signals not intended for all drives are marked as such by a note in [square brackets].

Information not available in any tech. reference I have access to. So I have used the known 34-pin floppy drive pinout, the actual 40-pin 95 XP floppy cable, and some measurement results to figure this out.

40-pin Floppy Cable Wiring Diagram (Model 95 XP, FRU P/N 33F8430)

PlanarFD0FD1FD2
111
2-92-92-92-9
10161010
111511
121412
131313
141214
151115
161016
17-3417-3417-3417-34
35-4011-16


44-pin Planar Diskette Interface (Media-Sense)

This connector is found on the 95A, Bermuda, Lacuna, 85 X, and 85 K/N planars. All floppy drives used must support media sense.

PinSignalPinSignal
1-2nd Drive installed [D0 & D1 pin 1]2Data rate Select 1
3+5 Vdc4Drive Type ID1/Drive status 1
5Ground6+12 Vdc
7Ground8-Index
9Drive Type ID0/Drive status 010Reserved
11Ground12-Drive Select 0 [D0 pin 12]
13Ground14-Security Command 0 [D0 pin 14]
15Ground16-Motor Enable 0 [D0 pin 16]
17Media Type ID1/Drive status 318-Direction In
19Ground20-Step
21Ground22-Write Data
23Ground24-Write Enable
25Ground26-Track 0
27Media Type ID0/Drive status 228-Write Protect
29Ground30-Read Data
31Ground32-Head 1 Select
33Data rate Select 034-Diskette Change
35Drive Select 1 [D1 pin 12]36Ground
37-Security Command 1 [D1 pin 14]38Ground
39-Motor Enable 1 [D1 pin 16]40-Drive Select 2 [D2 pin 12]
41Ground42-Security Command 2 [D2 pin 14]
43Ground44-Motor Enable 2 [D2 pin 16]

Signals not intended for all drives are marked as such by a note in [square brackets].

Information extracted from IBM PS/2 Servers 95 and 95A Technical Reference, Type 9595, page 2-5, First Ed., Sept 1993. P/N 71G3726

44-pin Floppy Cable Wiring Diagram (Model 95A, FRU P/N 92F0283)

PlanarFD0FD1FD2
111
2-112-112-112-11
12-1612-16
17-3417-3417-3417-34
35-3912-16
40-4412-16

44-pin Floppy Cable Wiring Diagram (Bermuda, FRU P/N 96F7756, P/N 41G9205)

This cable is electrically equivalent to the 95A cable but the physical construction is different (connector orientation and cable structure).

PlanarFD3FD2FD1
111
2-112-112-112-11
12-1612-16
17-3417-3417-3417-34
35-3912-16
40-4412-16

Content created and/or collected by:
Louis F. Ohland, Peter H. Wendt, David L. Beem, William R. Walsh, Tatsuo Sunagawa, Tomáš Slavotínek, Jim Shorney, Tim N. Clarke, Kevin Bowling, and many others.

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