ICL 1900 Series Computers

Each card is made of flexible plastic coated on one side with a layer of magnetic oxide, 16 inches long by 4½ inches wide and 0.0075 inches thick, with 64 parallel recording bands (128 tracks) running the length of the card giving a capacity of 165,888 alphaumeric characters.

Each card is individually addressable, the address being held as a pattern of notches in the top and bottom edges of the card, which are used by the selector mechanism to identify and withdraw the required card. The address pattern for each card is unique and completely independent of the card's location relative to other cards within the half magazine, eliminating the need to replace the card in its original location when returned to the magazine.

A magazine is divided into 2 decks of 128 cards, giving a storage capacity of 42.5 million alphaumeric characters per magazine.

There are 8 removable magazines per 1958/1 Retrieval Unit has a nominal on-line storage capacity of 340 million alphaumeric characters.

Fitting a 1958/2 Extension Unit to the 1958/1 Retrieval Unit doubles the capacity to 680 million alphaumeric characters (in 16 magazines).

A 1959 Control Unit can control up to 4 x 1958 Retrieval Units, giving a possible maximum nominal capacity of 2,720 million alphaumeric characters (16,384 cards in 64 magazines) - a vast online storage capacity in the 1960s.

A fore-runner of the MCF? - the NCR CRAM fitted to an NCR 315 computer system.