The notion of random-access memory wasn’t new, but every previous attempt was too slow to be practical. Under the guidance of Reynold B. Johnson, who would go on to become an IBM Fellow, team members hacked their way to a novel solution. The team tried rods, strips, tapes and flat plates before settling on an approach that involved magnetizing aluminum disks by coating them with iron oxide paint. Magnetic spots on each disk represented characters of data, and a magnetic arm — akin to a record-player needle — would read the spots as the disks rotated at blinding speed.
Getting the system to work required overcoming a number of technical, design and material challenges. The disks needed to be strong, absolutely flat, and light enough to be rotated by a motor. In the first trials, the disks warped at high speeds. Researchers responded by gluing two disks together. Unlike an actual record player needle, the magnetic arm couldn’t physically touch the disk, lest it destroy data. So researchers created a version that blasted out compressed air to keep the contraption hovering above the disk. Then came the issue of capacity. A single disk could not store enough data to be useful. So the team stacked 16 disks horizontally — disbelieving IBM executives referred to the unlikely design as the “baloney slicer.”
The final hurdle involved finding a way for the arm to reach the right place on the right disk instantly. “That was our goal: to go from any track, which was 6 inches in on a disk, out, down 2 feet to the bottom, and in 6 inches — in half a second,” Johnson recalled of the challenge. “We achieved something like 800 milliseconds, and that’s where the product came out.”
The resulting storage system could hold 5 million binary decimal encoded characters at 7 bits per character. The ultimate apparatus was the size of two kitchen refrigerators, weighed more than a ton, and stored 5 to 10 megabytes of data — the rough equivalent of a few of today’s MP3 files.
The name RAMAC was conceived by the researchers as an amalgam of “random-access memory” and the “AC” suffix of the UNIVAC computer, which was popular at the time. Marketers later altered the suffix to stand for “accounting and control" since demand for the unit initially stemmed from the need for real-time accounting in commerce. RAMAC immediately addressed the paralyzing overload of analog data in the enterprise, making it possible to access the data equivalent of 64,000 punched cards almost instantaneously.