Archive for August, 2019

Keeping history alive with a 1959 FACOM 128B relay-based computer

August 4, 2019 2 comments

Back in the 1950s, the competition was between vacuum tube (valve) based computers and their relay-based brethren. Whereas the former type was theoretically faster, vacuum tubes suffer from reliability issues, which meant that relay-based computers would be used alongside tube-based ones. Not surprisingly, Fujitsu also designed a number of such electro-mechanical computers back then. More surprisingly, they are still keeping a FACOM 128B in tip-top shape.

Known in the 1950s as Fuji Tsushinki Manufacturing Corporation, Fujitsu’s Ikeda Toshio was involved in the design of first the FACOM 100, which was completed in 1954, followed by the FACOM 128A in 1956. The 128B was a 1958 upgrade of the 128A based on user experiences. Fujitsu installed a FACOM 128B at their own offices in 1959 to assist with projects ranging from the design of camera lenses to the NAMC YS-11 passenger plane, as well as calculation services.

As a successor in a long line of electro-mechanical computers (including the US’s 1944 Harvard Mark I) performance was pretty much as good as it was going to get with relays. Ratings of the FACOM 128B were listed as 0.1-0.2 seconds for addition/subtraction operations, 0.1-0.35 seconds for multiplication, with operations involving complex numbers and logarithmic operations taking in the order of seconds. Maybe not amazing by today’s (or 1970s) standards, but back then their point was to massively and consistently outperform human computers, with (ideally) unfailing accuracy.

Today, this same FACOM 128B can be found at the Toshio Ikeda Memorial Hall at Fujitsu’s Numazu Plant, where it’s lovingly maintained by the 49-year old engineer Tadao Hamada. Working as the leader of Fujitsu’s 2006 project to pass down technology that is still historically relevant, his job is basically to keep this relay-based computer working the way it has done since it was installed in 1959.

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