Nostalgia buffs who lived through computing in the 1970s will enjoy some magnificent photos shared in a blog post by Ryszard Milewicz. These photos give three views of a ferrite core memory plane. The photo from this blog is a part of one of Mr. Milewicz’ close-up photos.
For those who were not exposed to core memory, this technology was based upon an approach in which every individual bit of a computer’s memory was a tiny donut made of compressed iron powder (“Ferrite”) that had to be hand strung with copper wire into a plane of bits.
A co-worker of The Memory Guy once had a high-speed core memory array that he used as a paperweight. Since it was high speed the currents were so great that the array had to be fan cooled. This example (and I wish I had a picture of it) was an 8×8-bit array on each of 8 stacked planes that made a 512-bit cube that fit over the top of a dedicated 3″ muffin fan. The whole array was housed in plexiglass so you could see all the bits right in front of you.
The cores would actually move slightly on the wires as they were magnetized and demagnetized. Computer lore told stories of programmers who wrote code that would jiggle the cores to musical pitches so that a computer would play a song without any need for a loudspeaker.
Once LSI (Large-Scale Integration – chips that held thousands or tens of thousands of transistors) came along transistor memories in the form of SRAM could be manufactured less expensively than could these core memories, and core became obsolete.
The Computer History Museum in Silicon Valley has numerous examples of core memory planes. These are almost worth the visit by themselves
Objective Analysis doesn’t cover core memories, but we do a lot of work on contemporary and future memory technologies (NAND, DRAM, SRAM, and NOR, right up to PCM, MRAM, and ReRAM.) Give us a shout of we can help you with a memory-related issue.