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Memory

Apollo Guidance Computer core rope memory

Fixed program storage woven by hand: a wire threading a core stores a one, a wire bypassing it stores a zero. Six modules of 512 cores and 192 sense lines each give 98 304 bit per module.

Manufacturer
MIT Instrumentation Laboratory / Raytheon
Architecture
Transformer read-only rope
Introduced
1966
Word size
15 bit
Width
98 304 bit
Count
512
Capacity
24 576 words
Capacity
6144 words
Type
Core rope (woven transformer read-only memory)
Record status
approved

Figures

Apollo Guidance Computer core rope memory: recorded figures
Metric Value Evidence Basis Method Source
Memory capacity (words) memory 36 864 words Confirmed Vendor-rated Design capacity Stated by the vendor Six rope modules; total fixed read-only capacity of the Block II computer. A word is 15 bit plus parity. Converting this capacity to bytes needs the word width and is published as a derived claim, never as a unit conversion.

Derived comparisons

18×

Formula
a ÷ b ratio v1
Inputs
  • agc-core-rope Memory capacity (words): 36 864 words
  • agc-erasable-core Memory capacity (words): 2048 words
Rounding
half-up , 4 significant digits

Compares memory-capacity-words at memory scope, obtained by design-capacity. Valid only within this comparability group, and reported to 4 significant digits — the precision of the least precise input.

Fitted to

Editorial notes

Block II raised the rope capacity from Block I's 24 576 words to 36 864 words. Address decoding is built into the wiring, which is why its cycle time is no shorter than the erasable memory's despite being read-only.

Sources