NCR CRAM

CRAM, or Card Random Access Memory, model 353-1, was a data storage device invented by NCR, which first appeared on their model NCR-315 mainframe computer in 1962. It was also available for NCR's third generation NCR Century series as the NCR/653-100.

A CRAM cartridge contained 256 3x14 inch cards with a PET film magnetic recording surface. Each "deck" of cards could contain up to 5.5 MB of alphanumeric characters. The cards were ingeniously suspended from eight d-section rods, which were selectively rotated to release a specific card, each card having a unique pattern of notches at one end. The selected card was dropped and wrapped around a rotating drum to be read or written. Each cartridge could store 5.5 MB.

Later versions of the CRAM, the 353-2 and 353-3, used decks of 512 cards, thus doubling the storage capacity of each unit.

Each card contains seven tracks containing 1550 slabs (12 bits each). Normally the track was initialized with a four slab header containing the cartridge number (two slabs), the card number and the track number.