Technology History | 99 Notre Dame Avenue — Fifty Spinning Discs and a Head That Floated on Air

Fifty aluminium discs, twenty-four inches across, stacked on a spindle turning at 1,200 revolutions a minute. That was the IBM 350 disk file, and it was worked out in a rented building at 99 Notre Dame Avenue in downtown San Jose. IBM opened the laboratory in 1952 on ground overlooking a plum orchard, in a part of California that had not yet been given a nickname. The lab was Reynold Johnson's. A former high school science teacher, he was sent west with instructions to find a site, do his own recruiting, and keep the staff under fifty. He signed a five-year lease on the Notre Dame Avenue building, advertised for engineers in the local papers, and had roughly thirty people working by that July. The problem they were handed was access. Business data lived on punched cards and magnetic tape, which meant reading through everything in front of the record you actually wanted. The team tried rods, strips, tapes and flat plates before settling on aluminium discs painted with iron oxide. Early discs warped at speed, so they glued them together in pairs. The reading head could not touch the surface without destroying data, so they floated it on compressed air. One disc held too little to be useful, so they stacked them, and IBM executives who saw the design called it the baloney slicer. The last problem was seek time. Johnson's target was to cross the whole stack and settle within half a second, and he later said the team reached something like 800 milliseconds, "and that's where the product came out." The finished unit stored five million characters, about the contents of 64,000 punched cards, weighed more than a ton, and shipped inside the IBM 305 RAMAC. Its announcement date is genuinely muddled: 4, 13 and 14 September 1956 all circulate, and IBM's own published history of the machine gives no day at all. What is not in doubt is when it shipped. The first system went to the Zellerbach Paper Company in San Francisco in June 1956, months ahead of any of those announcement dates. Today the building at 99 Notre Dame Avenue still stands, and the IEEE records it as a San Jose historic landmark. Do not plan a visit around the plaques, though. According to the IEEE's own milestone page, the marker, the ASME landmark plaque and the historical display were all taken into storage by the building's owner, to go back up when the building is leased again. A restored RAMAC actuator and disc stack sits in the Computer History Museum's storage gallery in Mountain View. The photograph shows a 305 RAMAC in service, with the disc stack visible through the cabinet window. Sources: IBM Heritage; Computer History Museum Storage Engine; IEEE ETHW RAMAC milestone and the 1984 ASME landmark brochure. Photo: Norsk Teknisk Museum, CC BY-SA 4.0, via Wikimedia Commons.