• From an early Ampex VCR
  • From a CDC 6600 computer. photo of the ghost in the machine...
  • the oldest one, of unknown origin, with the biggest cores and hand-wound toroids at the bottom as part of the read-write circuitry
  • from a mainframe. They used sticky paper to hold an array of cores for automated wiring. It took a lot of hand rework to fix errors.
  • Xak 4292. It has 300 bits in the memory array, with 15 pairs of rows with 10 ferrite cores in each row. close up photo

Core Memory Room

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We pulled the core memories into one conference room, and they really look good together.

This was the industry standard for electronic memory before DRAM and SRAM and Flash. Data was stored in the magnetization, or not, of each ring. It is a non-volatile memory, and relatively immune to radiation and soft errors, much like MRAM today.

Many of the rectangular patches are 4K bits. The early ones were woven by hand, and over the years the iron ring sizes shrank and became tightly woven into an electromagnetic fabric.

jeany777, born1945, js.brain, drona, and 14 other people added this photo to their favorites.

  1. jurvetson 19 months ago | reply

    some cool details, from the oldest one with the biggest cores, stitched by hand:
    What's That? (5)

    This one has some unusual wiring in the left section:
    Primitive Memories

    Late model (maybe into the 80's) with a tapestry of tightly woven cores, from a fully automated loom. It's a huge board with 1.5 Mbits in total:
    Solar Flair

    The core memory planes are typically stacked into a 3D box, like this one from the Apollo flight computer:

    Apollo Lunar Modules

    The magnetic cores within still hold whatever program they had when powered down. Since there are no tapes or archives of the code, it is possible that the only remaining copy of the Saturn V flight program is in cores like this.

    This module holds 114k bits (14 planes with a 128 x 64 fabric of ferrite donuts)... encoding 13-bit instructions, with the first triple-redundant logic. Ultrasonic delay line cache. Destructive readouts. Failure is not an option.

  2. nimosm 19 months ago | reply

    When I was a kid I asked a university computer studies student about how computers worked and he talked about magnetic rings. I never heard about them again until just now.

  3. seatonsnet 19 months ago | reply

    I am being initiated into the poetry of electronics.

  4. born1945 19 months ago | reply

    This is a cool display.

    The first computer I operated in the US Navy had ring storage. I can recall seeing the rings and the threaded wires. The computer was a Univac, part of the NTDS system. This was in the early 1970s.

  5. McPHX 19 months ago | reply

    I work for Honeywell, we have a similar display in the halls of my office.

  6. js.brain 19 months ago | reply

    I have seen those fancy core memories, but I was never able to touch them! I started to build electronics projects in the 1990s, of course with totally different memories... :-)

  7. Niall Oswald 19 months ago | reply

    What I'd like to know is whether the people working with these ever dreamed that one day, we'd have thousands of times the capacity of these great ferrite tapestries on something the size of a little fingernail?

    In 30 years' time, how clunky will today's technology seem? That's what I'm excited to discover.

  8. Chucil 19 months ago | reply

    Thank you for sharing!
    If the hand-stitched pattern is taken to Iran, maybe someone there could weave a distinguished and beautiful Persian rug based on it.

  9. winio_janik 19 months ago | reply

    the one from a vcr is probably few vide lines memory to delay lines for sync purposes

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