Core Memory

Long long ago.

Back when Bill Gates was still wearing diapers!

Computer memory was made using small ferrite rings called cores. The technology was called core memory. Here are a few pictures of what it looked like.

Enjoy!

(please respect my copyright by not using these for commercial purposes without my permission)

A description of how core memory worked is available here.

A closeup of a plane of core memory. Each of these dark grey iron cores stores a single bit of information.

Here's a plane of core memory with a ruler along the top. The marks on the ruler are one millimeter apart.

Here's the same plane of core memory from slightly further away. The wire loops at the left and the right are the sense wires that run through each core. Although only one sense wire per core was required, this core memory has two sense wires per core. Although I'm not sure why, this could have been to provide a higher level of reliability or sensitivity. Also visible in this photo are the wires that run up and down through each column of cores and left to right across each row of cores. Notice that each core is a pair of these straight wires through it that is unique to that core (i.e. no other core has the same pair of straight wires through it). These wires were used to set or reset the value of each core. If you look carefully, you may also be able to see that there are more layers of core below the top one that is most visible. There are actually eight layers of core planes here with each layer representing one of the bits in a byte.

Daniel Boulet