On 18/04/02 at 00:04 Dexter wrote: >> It is all explained in Keith Mitchell's hardware docs. Every other line >> in the ribbon is an earth. By twisting lines 10 through 13 you are >> swapping the drive 0 with the drive one signal with the earth line as a >> pivot. Quite what the PC one does is not clear.
>As I understand it, there are two drive select lines, allowing selection >of one from 4 drives, so on a PC cable they flip those, and their grounds. Actually, originally the shugart standard (inherited from 8" drives) had 4 drive selects and one motor on signal. When drives still had jumpers, you could choose which one of the 4 selects to use, and wether drive select also implies motor on, motor on is only alowed on a selected drive, or the drive will turn on the motor when the motor on signal is active, regardless of select signals. On the PC the drive was jumpered to use select 1. There are two motor on and two drive select signals, but they are set to the actual 4 signal pins of the standard, and actual selection has to be handled by twisting the cable because that way the correct select and motor on appear where the drive expects them. These days drives do not have jumpers any more. there are two selects and two motor on's, the correct combinatiopn is achieved using a twist in the wire (the unused select and motor on end up on unused pins on the drive, that once used to be select 2, 3, 4). The twist for miracle drives may actually be for SGC, so you can use the right angle connector for drive 1 and 2 instead of 3 and 4. Nasta
