The first time I encountered data loss and recovery effects of magnetic memory was as a night and weekend computer operator for the computer science department of Carnegie-Mellon University in the 1973-1974 time frame. Part of my job involved dealing directly with outages and failures associated with magnetic memory components used in what, at the time, were large computer systems. On occasions, portions of magnetic core memory or disk drives would encounter various failure modes and the systems using these devices would have to be reconfigured to operate without the failed components until repair personnel could come in to repair them, typically during normal business hours on weekdays. In the early hours of one Sunday morning, I was having such problems with a magnetic core memory module (a cabinet about 6 ft. high and 3 ft. across), and after awakening the manager in charge was instructed to restart the memory and continue the operation of the computer, setting a particular value into a particular memory location to cause the system to continue operation. After several such incidents within a period of less than an hour, a more definitive outage was produced after a mechanical impulse was applied to the cabinet, the memory was reconfigured out of the system, the system operated at reduced memory until the next weekday, and no further outages were experienced.
"The Science of Digital Forensics: Recovery of Data from Overwritten Areas of Magnetic Media,"
Journal of Digital Forensics, Security and Law: Vol. 7
, Article 1.
Available at: http://commons.erau.edu/jdfsl/vol7/iss4/1