Floppy Disk Drive Cable Termination and Device Addressing
Cable Termination
Similar to the SCSI interface, the standard IBM PC floppy disk drive bus needs termination at each end, which is achieved by fitting a 150-ohm resistor network to a socket provided on the last drive on the cable (and similarly on the controller card) such as the Beckman 899-3-R150.
Device Addressing
The IBM PC floppy disk drive bus includes the facility for up to four drives to be daisy-chained, with device addressing being controller by pins 6, 10, 12 and 14. Initially, jumpers were used to manually select the device ID (0 through 3) with a flat ribbon cable.
Another option is a 'twisted' ribbon cable, where the cables serving pins 6 to 14 are reverse between the first and sector drive connector, thereby providing 'cable select' addressing for two devices (only). Using this method, both drives should be jumpered to drive 1 (DS1), with the drive connected to the first (untwisted) connector being drive 1, and the drive connected to the second (twisted) connector being drive 0 (DS0).