 Through mergers, ERA became a division of UNIVAC shipping the Series 1100 drum as a part of the UNIVAC File Computer in 1956; each drum stored 180,000 characters.The first mass-produced computer, the IBM 650, had about 8.5 kilobytes of drum memory (later doubled to about 17 kilobytes in the Model 4).As late as 1980, PDP-11/45 machines using magnetic core main memory and drums for swapping were still in use at many of the original UNIX sites.