IBM 1131 Central Processing Unit

The 1131 CPU was built into a free-standing, desk-like enclosure. It included a standard keypunch-type keyboard and Selectric printing mechanism, which wasn't usually used much unless the system ran APL. The CPU logic and core memory were in the back of the "desk" and the power supply and space for a single disk drive were at the right, where the desk drawers would be. Models were available with or without disk storage, with memory cycle speeds from 5.7 microseconds to 2.2 microseconds, and with 4KW to 32KW core memory (that is, 8KB to 64KB). The 5.7-microsecond system was actually too slow to service the 1132 Printer; see the "Printing" page for a story about that.