CRAM
Encyclopedia
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.
A CRAM cartridge contained 256 3x14" 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 5.5MB. Later versions of the CRAM; 353-2 and 353-3 used Decks of 512 card, thus doubling the storage capacity of each unit. The CRAM was also available on NCR's third generation NCR Century 100
as the NCR/653-100.
Each card contains seven tracks containing 1550 slabs each of them. Normally the track was initialized with a four slab
header containing the cartridge number (2), the card number
and the track number.
Cards were dropped by changing the card rods to a binary configuration and release the two outside release rods. Air was blown over the top of the cards to keep them separated, and to increase the dropping speed. Once on the rotating Drum a series of positive and negative air pressure chambers pulled the card across a magnetic read-write head. After one or more passes over the head, where data is written to or read from the card, a release gate allow the card to be thrown along a raceway over the card deck, and onto a ‘’loader’’ mechanism. The loader used a group of electro-magnetic solenoids to slam the card back onto the control rods. The unit was a monster with two large electric motors that drove four large vacuum/blowers. It was possible to have up to five cards in motion at any point in time; one dropping, one on the drum, two in the return transport, and one being loaded back onto the deck.
If the card didn't succeed in dropping there was a "magic wand" similar to a pencil available to solve the problem.
One feature of this device was the potential for a "double drop", where two cards would drop at once, due to a break in a notch on one card, or, more commonly, a card being held by one rod being dislodged by the adjacent card dropping, usually cards 000 (the deck directory card) and 001 which resulted in the necessity of recreating the directory. This would result in a high pitched noise with which operators were very familiar and could hear even outside the computer room, and damage to the cards.
Another interesting feature was that, should an operator accidentally drop all the cards from a cartridge, they could be replaced without worrying about order. The order of the cards was not important because of the notch encoding system.
CRAM was very successful in the 1960s, offering a fast and secure storage alternative to magnetic tape
, but was superseded by the development of superior disk drive technology.
Data storage device
thumb|200px|right|A reel-to-reel tape recorder .The magnetic tape is a data storage medium. The recorder is data storage equipment using a portable medium to store the data....
invented by NCR
NCR Corporation
NCR Corporation is an American technology company specializing in kiosk products for the retail, financial, travel, healthcare, food service, entertainment, gaming and public sector industries. Its main products are self-service kiosks, point-of-sale terminals, automated teller machines, check...
, which first appeared on their model NCR-315 mainframe computer
Mainframe computer
Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...
in 1962.
A CRAM cartridge contained 256 3x14" cards with a PET film
PET film (biaxially oriented)
BoPET is a polyester film made from stretched polyethylene terephthalate and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aroma barrier properties and electrical insulation.A variety of companies manufacture boPET and other...
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 5.5MB. Later versions of the CRAM; 353-2 and 353-3 used Decks of 512 card, thus doubling the storage capacity of each unit. The CRAM was also available on NCR's third generation NCR Century 100
NCR Century 100
The NCR Century 100 was NCR's first all integrated circuit computer. The 615-100 Series integrated a complete data processing system had 16KB or 32KB of short rod memory, 80-column card reader or paper tape reader, two 5MB removable disc drives, 600-line per minute printer. You could have a punched...
as the NCR/653-100.
Each card contains seven tracks containing 1550 slabs each of them. Normally the track was initialized with a four slab
Slab
-Physical materials:* Slab , a length of metal* Concrete slab, a flat plate used in construction* A piece of stone or concrete used to pave sidewalks or road surfaces* Slab : That portion of a tectonic plate that is subducting...
header containing the cartridge number (2), the card number
and the track number.
Cards were dropped by changing the card rods to a binary configuration and release the two outside release rods. Air was blown over the top of the cards to keep them separated, and to increase the dropping speed. Once on the rotating Drum a series of positive and negative air pressure chambers pulled the card across a magnetic read-write head. After one or more passes over the head, where data is written to or read from the card, a release gate allow the card to be thrown along a raceway over the card deck, and onto a ‘’loader’’ mechanism. The loader used a group of electro-magnetic solenoids to slam the card back onto the control rods. The unit was a monster with two large electric motors that drove four large vacuum/blowers. It was possible to have up to five cards in motion at any point in time; one dropping, one on the drum, two in the return transport, and one being loaded back onto the deck.
If the card didn't succeed in dropping there was a "magic wand" similar to a pencil available to solve the problem.
One feature of this device was the potential for a "double drop", where two cards would drop at once, due to a break in a notch on one card, or, more commonly, a card being held by one rod being dislodged by the adjacent card dropping, usually cards 000 (the deck directory card) and 001 which resulted in the necessity of recreating the directory. This would result in a high pitched noise with which operators were very familiar and could hear even outside the computer room, and damage to the cards.
Another interesting feature was that, should an operator accidentally drop all the cards from a cartridge, they could be replaced without worrying about order. The order of the cards was not important because of the notch encoding system.
CRAM was very successful in the 1960s, offering a fast and secure storage alternative to magnetic tape
Magnetic tape
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...
, but was superseded by the development of superior disk drive technology.