Complex sentence: Hard disks offered for the Model II also used a terminating resistor pack; these were sold as master and slave drives, with the master hard disk (which had the resistor pack) needing to be the last one on the chain.
Split into simpler sentences: Hard disks offered for the Model II also used a terminating resistor pack. These were sold as master and slave drives, with the master hard disk (which had the resistor pack) needing to be the last one on the chain.