The S-100 Expansion Unit plugged into the back of the Sorcerer via a cable and allowed the use of up to six different S-100 cards.  The Expansion unit was vital for power users that wanted to do any serious computing on their Sorcerer via CP/M.  Although a standalone disk drive unit was also made for CP/M users, the S-100 Expansion Unit was the ultimate in expandability.  The S-100 Expansion Unit retailed for $419 in 1980.