Floppy Drive Interface Pinouts
The rising champion of Micro Channel, Tomáš Slavotínek, hefted his mighty multimeter, bellowed his defiance to the dark gods of Obscurity and Uncertainty, and hewed down some mighty servants of Kaos.

He verified some pinouts and cranked out some graphical depictions of some common floppy cables.

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

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 16 -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 +5VDC
39 Ground 40 +12VDC

34-pin Header Interface (Non-Media Sense)

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

Pin Signal Pin Signal
1 Ground 2 -High Density Select
3 + 5VDC 4 Drive Type ID 1
5 Ground 6 + 12VDC
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 + 5VDC 4 Drive Type ID1/Drive status 1
5 Ground 6 + 12VDC
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

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

Pin Signal Pin Signal
1 -2nd Drive installed [D0 & D1 pin 1] 2 Data rate Select 1
3 + 5VDC 4 Drive Type ID1
5 Ground 6 + 12VDC
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 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

   This connector is found on the 95A, Lacuna, and 9585 K-N models. 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 + 5VDC 4 Drive Type ID1/Drive status 1
5 Ground 6 + 12VDC
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 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


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