I'm forwarding a blog post written by a member of the CHM 1401 Restoration Team. Excellent description (with pictures) of how 1401 memory is addressed, etc.: http://www.righto.com/2015/10/repairing-50-year-old-mainframe-inside.html Cheers, Lyle -- 73 AF6WS Bickley Consulting West Inc. http://bickleywest.com "Black holes are where God is dividing by zero"