IBM 701 Plug-in Unit
The 701's vacuum tubes were collected into "pluggable units", a concept introduced with IBM's 604. The 701 was developed in 1952 in the Poughkeepsie Laboratory. The 701 known as the Defense Calculator. The 701's used 18-bit instructions, with maximum, memory of 4096 words of 36-bits. It used Williams tubes or magnetic core memory which had a cycle time1 of 12 microseconds, and could do 2000 Multiplies and Divides per second.
|figures 3 and 4|