The first version of the Apollo guidance computer had a ROM of only 12 K words of 16 bit. Later it was doubled to 24 K and finaly tripled to 36 K words.

The first version of core rope read only memory used one core for 4 words of 16 bits, so one core for 64 bits alltogether. 3072 cores to store 12,288 words of 16 bits.

From this page by Brent Hilbert:

Some writings suggest this was accomplished by doubling and tripling the number of sense loops through the cores, so cores would be woven with 8, then 12 words each.

If this is true, the number of bits per core was increased to 128 and finaly to 192.

The first version had 20 inhibit lines, 2 set/reset lines and 4*16 sense lines, 2*10+2+4*16=86 wires alltogether through a single core. The maximum number of wires per core was increased later from 86 to 150 to 214. Still 3072 cores for 36.864 words.

Up to 214 wires woven through a single small core, is it really true?

enter image description here

Photograph © Raytheon, from the files of Jack Poundstone. From Visual Introduction to the Apollo Guidance Computer.

From this NASA page:

The memory in Block II consisted of a segment of erasable core and six modules of core rope fixed memory.

If there are six ROM modules, the total number of cores should be 6144 (1024 cores per module) and up to 118 wires per core. 96 bits per core for 36.864 words of 16 bits.

  • 1
    $\begingroup$ I think this would be better suited for our friends at Retrocomputing $\endgroup$ – asdfex Dec 29 '18 at 18:45

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