# ST506/412

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.
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.

(At the controller)
(At the controller)

(At the harddisk)
(At the harddisk)

34 PIN IDC MALE at the Controller.
20 PIN IDC MALE at the Controller.

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

## 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
16 | RES | (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

## Data connector

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