@aml's comment under @OrganicMarble's answer to the question Did the IBM System/4 Pi computer have radiation-hardened versions for Skylab and Shuttle? says:

@uhoh- according to wikipedia, the AP-101B used magnetic core memory (because it was fully matured technology in the late 1970's).

I'd only heard of core memory used on spacecraft within the context of the Apollo missions to the Moon. Now that I can read in this archived documentation, (PDF) that core memory was used in flight computers in the following decade, so I'd like to ask:

Question: Has magnetic core memory been used beyond cis-lunar space?


The TC computer utilizes an 8,192 word by 8 bit destructive readout core memory. The memory has a 2.5 microsecond read-write cycle time. Each cycle consists of a read followed by a write operation. The computer initiates a start memory every three microseconds. The access time of the memory is approximately. 9 usec. A coincident current (3-D) selection scheme is utilized. The memory array requires our memory mats packaging two bits per mat. Operation is possible over the ambient temperature range of -55 C to +l00C.


The main storage array is fabricated from core planes which are a militarized version of planes used on the IBM System/360. Each plane has 16,384 cores. Planes are conformally coated and foam padding is placed between planes for environmental protection of cores.

later still:

Read Only Storage is implemented with a microminiature linear ferrite 7/12 (ID/OD in mils) magnetic core. The basic core plane contains 512 by 70 cores. A core is located where a "1" bit is stored and a core is missing where a "0" bit is stored. Two wires thread each core: one drive winding and one sense winding. Two planes are required for the ROS. Monolithic circuits are used in the decode. driver. detector and latch portion of the ROS.

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    $\begingroup$ An interesting follow-up question would be whether any company still makes core memory. However, probably no SE site would take such a question as on-topic. $\endgroup$
    – DrSheldon
    May 9, 2019 at 15:37
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    $\begingroup$ retrocomputing.se $\endgroup$
    – Hobbes
    May 9, 2019 at 16:33
  • $\begingroup$ @Hobbes: One would think so. Yet their meta site had a recent post complaining that too many things were on-topic. uhoh wrote a clever comment there that made me laugh: retrocomputing.meta.stackexchange.com/questions/739/… $\endgroup$
    – DrSheldon
    May 9, 2019 at 21:18
  • $\begingroup$ @DrSheldon that is a beautiful answer; bravo! $\endgroup$
    – uhoh
    May 9, 2019 at 23:42

1 Answer 1


It has been used all the way to the edge of the solar system:

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    $\begingroup$ The article linked from the Wiki page about plated-wire memory suggests the author's Univac is the last such machine operating in the world, but it's not the last one in the universe. $\endgroup$
    – supercat
    May 9, 2019 at 22:49

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