A database of SMS cards: The technology inside IBM’s 1960s mainframes

Ken Shirriff writes:

Although the original idea of SMS cards was to standardize on a few types, the number of different cards exploded as time went one, resulting in thousands of different SMS card types. As well as logic gates, SMS cards can have an amazing variety of functions such as an oscillator, voltage regulator, core memory, fuses, printer hammer driver, disk speed detector or temperature switch. The 1401 computer alone uses 162 different types of SMS cards.

Information on particular SMS cards is surprisingly hard to find, so I made a database of SMS cards, collecting information on 900 different cards. Given the historical importance of SMS cards, I think information on this technology should be preserved. I pulled together information from scans of old IBM documents and a bunch of other sources (which was more work than I expected). You can access the database at righto.com/sms and see the wide variety of cards along with photos, descriptions, schematics, and the devices that use them.

More details at Ken Shirriff’s blog.