CRAM, DataCell, and 3850

Magnetic drums tend to be used either for computer memory, or swap space. Of course, a drum is equivalent to a head-per-track disc. Discs of the type used in today's computers, though, have too much in the way of thermal expansion issues to be made head-per-track.

Regular disk drives, starting with IBM's original RAMAC - which, by the way, had a capacity of about 10 megabytes, that of the hard disk in the IBM PC XT - are usually used, instead, for storing files that can be read by programs as if they were decks of punched cards, or magnetic tapes.

The disk, however, is an expensive form of storage. So there had been attempts to store large quanbreasties of data in an on-line fashion that was less expensive, at the cost of the initial request for the data being slower.

There was NCR's CRAM, where strips of magnetic material were selected in a manner reminiscent of edge-notched cards. Initially, the cards had seven tracks of data, and a total capacity of 21,700 characters per card, the characters presumably being 6-bit characters.

The device could only handle 256 cards at a time.

I suspect NCR came out with improved versions later, because I believe CRAM was around for quite a while.

The IBM 2321 DataCell was doubtless inspired by NCR's CRAM. It had a larger capacity; magnetic strips each having a capacity of 2 megabytes were stored on a carousel which contained 200 of them.

Then there was the IBM 3850 Mbutt Storage System. Instead of strips of magnetic material, spools of tape, each one containing 50 megabytes of data, were stored in a vast honeycomb.

In today's era of 120 GB hard disks, it would seem there is little reason for resorting to such technologies any longer.

However, magnetic tape still is in use, and today's format involves a small square cartridge - which presumably lends itself well enough to automated tape libraries.

Neither the 3850 nor the DataCell was a roaring success for IBM, and Hypertape was particularly unsuccessful. Version II sold to two customers, one of them the IRS, and the only customer for Version I was Canada's equivalent of the IRS.

Apparently, the DataCell had reliability problems, while NCR's CRAM was both successful and reliable in practice. Reliability is very important for the place where important data is kept, even if everything should be backed up on a tape somewhere.

John Savard Usenet Zone Free Binaries Usenet Server More than 140,000 groups Unlimited download