NCR CRAM

Lore & Background

A CRAM cartridge contained 256 cards with a PET film magnetic recording surface, each card suspended from eight d-section rods. The rods were selectively rotated to release a specific card, which was dropped and wrapped around a rotating drum for reading or writing. Air was blown over the cards to keep them separated and increase dropping speed. Positive and negative air pressure chambers pulled the card across a magnetic read-write head. After one or more passes, a release gate allowed the card to be thrown along a raceway onto a loader mechanism, which used electromagnetic solenoids to place the card back onto the control rods. The unit had two large electric motors driving four vacuum/blowers, and up to five cards could be in motion at once.

Problems included 'double drops' (two cards dropping at once), often due to a break in a notch or a card being dislodged by an adjacent card dropping. This produced a high-pitched noise called a 'screamer' and could damage cards. Cards that would not drop were called 'hangers'. A 'magic wand' similar to a pencil was available to solve a card that did not drop. The order of cards was not important because of the notch encoding system; if all cards were accidentally dropped, they could be replaced without worrying about order.

Reader's Guide

CRAM was notable for providing random access to data at a time when magnetic tape was the primary storage medium, offering faster retrieval and greater security. Its success in the 1960s demonstrated the viability of card-based random-access storage for business computing. However, the development of superior disk drive technology eventually rendered CRAM obsolete. The system's mechanical complexity—with dropping cards, rotating drums, and pneumatic transport—was both a strength and a vulnerability, as evidenced by the familiar 'screamer' incidents. Later versions (353-2 and 353-3) doubled storage capacity by using 512-card decks, extending the product's life into the NCR Century series. Despite its eventual replacement, CRAM represents an important step in the evolution from sequential tape storage to fully random-access disk systems.

Did You Know?

• Each CRAM cartridge could store 5.5 MB of alphanumeric characters.
• Cards were released by rotating d-section rods to a binary configuration and releasing two outside 'release' rods.
• A 'double drop' of two cards at once was called a 'screamer' due to the high-pitched noise it produced.
• The order of cards in a cartridge was not important because of the notch encoding system.