How much memory fit in a six-foot-tall cabinet in 1964?

IBM’s site has a blurb about the IBM 2361 core storage unit.

In each 2361, almost 20 million ferrite cores — tiny doughnut-shaped objects, each about the size of a pinhead — were strung in two-wire networks and packaged, with associated circuitry, into a cabinet only five by [two and a half] feet and less than six feet tall. The first memory was installed for use in a complex of five powerful IBM 7094 Model II data processing systems. Four additional memories were added to the NASA Real Time Computer Complex (RTCC).


The 2361’s design provided for storage of 524,000 36-bit words and a total cycle time of eight microseconds in each memory. The 2361 was the first IBM memory to use two-wire core storage to increase storage capacity, improve performance and reduce unit size.

Now, I don’t know if my math is correct, but here’s what it shows. 524,000 36-bit words means 18,864,000 bits. According to Google, 18 864 000 bits = 2.24876404 megabytes.

2.2 MB is nothing today. Imagine it! A box 5 ft x 2.5 ft x 6 ft, and it stores less than two standard 3.5″ floppy disks!
IBM Archives

Leave a Reply