Thursday, April 9, 2009

Holy Relic - Core Memory

I've recently been on a quest to find and begin digitally archiving the surviving history of the University of Texas at Austin's Computation Center, which was responsible for the academic side of computing on campus from 1958 until it was merged with our data processing and telecom shops into a new department called Information Technology Services (ITS) a handful of years ago. The result of that merger and the passing of time is that much of ITS seems never to have heard of the Computation Center, which did a lot of good work that shouldn't be forgotten.

While searching for copies of the Computation Center newsletters (none of which I had had the foresight to keep), the same colleague who seems to have the only existing set that is even potentially complete, revealed to me one of our forgotten holy relics: A core memory card from our Control Data Corporation Cyber 6600, or 6400 computers, or the extended core memory that they shared. Anyway, core memory.

The card, which measures 4.125 inches on each side, looks like this:

In extreme close-up you can see the ferrite rings (the "cores") that magnetically stored the data, supported by the matrix of fine wires (slightly thinner than a human hair) that run through the middle of the rings, allowing data to be written-to, and read-from, them. Each one stored a single bit of data. If I've counted correctly, this board stored 4,356 bits of data.

I remember our Cybers, but never did any work with them. However, years before joining the Computation Center, I did do much of my early programming on a Digital Equipment Corporation PDP-11/34 (running RSTS/E) that also used core memory.


  1. When I first looked at that picture, I thought it was a piece of embroidery with peacock feathers around the edges.

  2. Wow... amazing!

    Although my brain hurts now after reading the wiki article on what core memory is and how it works!