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 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 |
