Today, a paper-thin, magnetic-memory disk is a commercial reality. Just six months ago, the developmental ancestor of this flexible-disk memory made its debut at the Eastern Joint Computer Conference (ED, January 6, 1960).
At the Western Joint Computer Conference next week, the first commercial model of the LFE Bernoulli-Disk Data Storage Device will be shown. A 100,000-bit memory, the BD-103 is manufactured by the Computer Products Div. of Laboratory for Electronics, 10799 Commonwealth Ave., Boston.
On the surface of a 7-1/2 in. wide, 2-mil thick disk of oxide-coated Mylar, the memory has 40 tracks for data, clock pulses, revolver loops, and spares. A 1/20th-hp motor drives the disk at 3600 rpm, a 180-kc bit rate for each track. The air flowing between the flattened, rotating disk and the head plate helps maintain a 3/4-mil head-to-tape separation.
The read-write heads, spirally placed with about 30 heads to the radial inch, are mounted flush with the tape side of the head plate. The heads provide a read amplitude of 20 mv and require 250 ma of write current.
The entire package, including the memory, a cooling fan, a metal wrap-around, and a plastic dust cover, fits in a 9-in. cube and weighs 15 lb.
The BD-103, which sells for $4000, will be available on 90-to-120-day delivery for initial orders. It is the first in the BD-100 series of devices, which will include 100,000-bit memories for operation from 1800 to 8000 rpm for bit rates from 90 to 400 kc. Planned for sale in November of this year, the BD-1000 series devices will be a million-bit store. By the end of December, the BD-500, a 500,000-bit store should be available. (Electronic Design, April 27, 1960, p. 54)
In the Jan. 24 issue, we commented that for all practical purposes, this item seemed to be a floppy disk. Although the disk doesn't appear to be removable, and the multiple read-write heads are fixed, LFE certainly deserves to share some of the credit with IBM for the invention.
See associated figure
