Hardware pinouts information and cables schemes

ST506/412 pinout

hard drive connector

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Developed by Seagate. Also known as MFM or RLL since these are the encoding methods used to store data. Seagate originally developed it to support their ST506 (5 MB) and ST412 (10 MB) drives.

34 pin IDC male connector layout

34 pin IDC male connector
at the controller



The first drives used an encoding method called MFM (Modified Frequency Modulation). Later a new encoding method was developed, RLL (Run Length Limited). RLL had the advantage that it was possible to store 50% more with it. But it required better drives. This is almost never an problem. Often called 2,7 RLL because the recording scheme involves patterns with no more than 7 successive zeros and no less than two.

Second connector: 20 PIN IDC MALE at the Controller.
20 PIN IDC MALE

20 PIN IDC FEMALE at the Harddisk.
20 PIN IDC FEMALE

Control connector

Pin Name Description
2 Head Sel 8
4 Head Sel 4
6 Write Gate
8 Seek Complete
10 Track 0
12 Write Fault
14 Head Sel 1
16RES(reserved)
18 Head Sel 2
20 Index
22 Ready
24 Step
26 Drive Sel 1
28 Drive Sel 2
30 Drive Sel 3
32 Drive Sel 4
34 Direction In
Note: All odd pins are GND, Ground.

Data connector

Pin Name Description
1 Drive Selected
2GNDGround
3RES(reserved)
4GNDGround
5RES(reserved)
6GNDGround
7RES(reserved)
8GNDGround
9RES(reserved)
10RES(reserved)
11GNDGround
12GNDGround
13 Write Data+
14 Write Data-
15GNDGround
16GNDGround
17 Read Data+
18 Read Data-
19GNDGround
20GNDGround


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Pinouts.ru > Hard drives connectors pinouts listing >  Pinout of ST506/412 and layout of 34 pin IDC male connector and 34 pin IDC female connector
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