DEC G114B

16Kx18 UNIBUS Core Memory

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The first picture on this page shows the core plane of the DEC G114B core memory module (picture, 630x360, 29K bytes). This type of memory module was used in DEC PDP-11 computers with UNIBUS architecture. The core plane is quite fragile, so it is normally hidden under a fiber shield, which has been removed to take this picture.

The board has a capacity of 16384 machine words with 18 bits each. Since each bit is stored in a separate ferrite toroid, that makes a total of 294912 cores. The plane is divided into 36 sub-matrixes. Each matrix has a capacity of 8192 bits.

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Each sub-matrix of the core plane has 128 vertical rows and 64 horizontal rows. The second picture on this page shows two such matrixes. On the larger picture, the driver lines can be seen. However, the ferrite toroids are still too small to see, even though this picture already show the plane with some magnification.

Nils M Holm 2004, 2008