| Forum Home | ||||
| Press F1 | ||||
| Thread ID: 19272 | 2002-05-12 02:45:00 | Floppy cable 'twist' | Guest (0) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 48384 | 2002-05-12 02:45:00 | Why does the 2nd socket on a floppy drive have a twist on 7 wires? B drive? Bye | Guest (0) | ||
| 48385 | 2002-05-12 03:11:00 | The controller uses a few of the wires for 'Drive select' and 'motor enable' for each of two drives. The drives have (at least 5.25' drives all had) jumpers marked DS0, DS1, DS2, DS3 (and for those who like to be different: DS1, DS2, DS3, DS4). (When you had only 360k floppies, you could get a controller to handle four drives for your 'big' business files). A cable with the straight through connection needs the jumpers to be set differently on each drive. IBM decided to have all the drives set to DS1 (or DS2) by the drive manufacturer, to save assembly time (and errors) in the computer factory. The twist in the cable changes just the selection lines. The twist makes a DS1 mean DS0 : drive A:, another drive connected to the 'untwisted' cable will be 'B:'. So you have to have the A: drive at the very end of the cable. Just for fun and to add to the confusion, the 34 wire cables on the control cable for MFM hard disks also had a twisted section of cable (in a different set of lines). Otherwise the cables were identical. The drives didn't work if you used the wrong cable. |
Guest (0) | ||
| 48386 | 2002-05-12 03:40:00 | Thanks Graham - good explanation. Bye Peter | Guest (0) | ||
| 1 | |||||