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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

Pin	Signal	Pin	Signal
1	Ground	2	-High Density Select
3	Reserved	4	Reserved
5	Ground	6	Reserved
7	Ground	8	-Index
9	Ground	10	Reserved
11	Ground	12	-Drive Select
13	Ground	14	Reserved
15	Ground	16	-Motor Enable
17	Ground	18	-Direction In
19	Ground	20	-Step
21	Ground	22	-Write Data
23	Ground	24	-Write Enable
25	Ground	26	-Track 0
27	Ground	26	-Write Protect
29	Ground	30	-Read Data
31	Ground	32	-Head 1 Select
33	Ground	34	-Diskette Change
35	Ground	36	Ground
37	Ground	36	+5 Vdc
39	Ground	40	+12 Vdc

34-pin Header Interface

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

Pin	Signal	Pin	Signal
1	Ground	2	-High Density Select
3	+5 Vdc	4	Drive Type ID 1
5	Ground	6	+12 Vdc
7	Ground	8	-Index
9	Ground	10	Reserved
11	Ground	12	-Drive Select
13	Ground	14	Reserved
15	Ground	16	-Motor Enable
17	Ground	18	-Direction In
19	Ground	20	-Step
21	Ground	22	-Write Data
23	Ground	24	-Write Enable
25	Ground	26	-Track 0
27	Ground	28	-Write Protect
29	Ground	30	-Read Data
31	Ground	32	-Head 1 Select
33	Ground	34	-Diskette Change

Enhanced 34-pin Header Interface (Media Sense)

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

Pin	Signal	Pin	Signal
1	Ground	2	Data rate Select 1
3	+5 Vdc	4	Drive Type ID1/Drive status 1
5	Ground	6	+12 Vdc
7	Ground	8	-Index
9	Drive Type ID0/Drive status 0	10	Reserved
11	Ground	12	-Drive Select
13	Ground	14	-Security Command *
15	Ground	16	-Motor Enable
17	Media Type ID1/Drive status 3	18	-Direction In
19	Ground	20	-Step
21	Ground	22	-Write Data
23	Ground	24	-Write Enable
25	Ground	26	-Track 0
27	Media Type ID0/Drive status 2	28	-Write Protect
29	Ground	30	-Read Data
31	Ground	32	-Head 1 Select
33	Data rate Select 0	34	-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)

Pin	Signal	Pin	Signal
1	Reserved	2	-High Density Select
3	+5 Vdc	4	Reserved
5	Ground	6	+12 Vdc
7	Ground	8	-Index
9	Ground	10	Reserved
11	Ground	12	-Drive Select
13	Ground	14	Reserved
15	Ground	16	-Motor Enable
17	Ground	18	-Direction
19	Ground	20	-Step
21	Ground	22	-Write Data
23	Ground	24	-Write Enable
25	Ground	26	-Track 0
27	Ground	28	-Write Protect
29	Ground	30	-Read Data
31	Ground	32	-Head 1 Select
33	Ground	34	-Diskette Change
35	Ground	36	Ground
37	Reserved	38	+5 Vdc
39	Ground	40	+ 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.

Pin	Signal	Pin	Signal
1	-2nd Drive installed [D0 & D1 pin 1]	2	Data rate Select 1
3	+5 Vdc	4	Drive Type ID1
5	Ground	6	+12 Vdc
7	Ground	8	-Index
9	Drive Type ID0	10	-Motor Enable 1 [D0 pin 16]
11	Ground	12	-Drive Select 0 [D1 pin 12]
13	Ground	14	-Drive Select 1 [D0 pin 12]
15	Ground	16	-Motor Enable 0 [D1 pin 16]
17	Media Type ID1	18	-Direction In
19	Ground	20	-Step
21	Ground	22	-Write Data
23	Ground	24	-Write Enable
25	Ground	26	-Track 0
27	Media Type ID0	28	-Write Protect
29	Ground	30	-Read Data
31	Ground	32	-Head 1 Select
33	Data rate Select 0	34	-Diskette Change
35	Ground	36	Drive Select 2 [D2 pin 12]
37	Ground	38	Ground
39	Ground	40	-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)

Planar	FD0	FD1	FD2
1	1	1	—
2-9	2-9	2-9	2-9
10	16	10	10
11	15	11	—
12	14	12	—
13	13	13	—
14	12	14	—
15	11	15	—
16	10	16	—
17-34	17-34	17-34	17-34
35-40	—	—	11-16

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.

Pin	Signal	Pin	Signal
1	-2nd Drive installed [D0 & D1 pin 1]	2	Data rate Select 1
3	+5 Vdc	4	Drive Type ID1/Drive status 1
5	Ground	6	+12 Vdc
7	Ground	8	-Index
9	Drive Type ID0/Drive status 0	10	Reserved
11	Ground	12	-Drive Select 0 [D0 pin 12]
13	Ground	14	-Security Command 0 [D0 pin 14]
15	Ground	16	-Motor Enable 0 [D0 pin 16]
17	Media Type ID1/Drive status 3	18	-Direction In
19	Ground	20	-Step
21	Ground	22	-Write Data
23	Ground	24	-Write Enable
25	Ground	26	-Track 0
27	Media Type ID0/Drive status 2	28	-Write Protect
29	Ground	30	-Read Data
31	Ground	32	-Head 1 Select
33	Data rate Select 0	34	-Diskette Change
35	Drive Select 1 [D1 pin 12]	36	Ground
37	-Security Command 1 [D1 pin 14]	38	Ground
39	-Motor Enable 1 [D1 pin 16]	40	-Drive Select 2 [D2 pin 12]
41	Ground	42	-Security Command 2 [D2 pin 14]
43	Ground	44	-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)

Planar	FD0	FD1	FD2
1	1	1	—
2-11	2-11	2-11	2-11
12-16	12-16	—	—
17-34	17-34	17-34	17-34
35-39	—	12-16	—
40-44	—	—	12-16

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).

Planar	FD3	FD2	FD1
1	1	1	—
2-11	2-11	2-11	2-11
12-16	12-16	—	—
17-34	17-34	17-34	17-34
35-39	—	12-16	—
40-44	—	—	12-16

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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