Redditor finds legendary computer from 1956 in his grandparents' basement

Redditor finds legendary computer from 1956 in his grandparents’ basement

The LGP-30 computer, from 1956, that c-wizz found in the basement.
Enlarge / The LGP-30 computer, from 1956, that a Redditor found in a basement.

On Monday, a German Redditor named c-wizz reported finding a very rare 66-year-old Librascope LGP-30 computer (and several 1970 DEC PDP-8/e computers) in their grandparents’ basement. The LGP-30, first released in 1956, is one of only 45 made in Europe and is perhaps best known as the computer used by “Mel” in a famous piece of hacker lore.

Developed by Stan Frankel at the California Institute of Technology in 1954, the LGP-30 (short for “Librascope General Purpose 30”) originally sold for $47,000 (about $512,866 today, adjusted for inflation) and weighed 800 pounds. Even so, people considered it a small computer back then due to its desktop size (about 44×33×26 inches). According to, the LGP-30 included 113 vacuum tubes, 1,450 semiconductor diodes and a rotating magnetic drum memory – a tube 6.5 inches in diameter and 7 inches long spinning at 3,700 rpm. /min – which could store 4,069 31-bit words (equivalent to about 15.8 modern kilobytes).

In addition to the LGP-30 main unit, c-wizz found a Flexowriter typewriter-style console (used for input and output with the machine) and what looks like a paper tape drive for storage external data. A few PDP-8/e machines and some related equipment were hiding nearby. “There seem to be more mods belonging to PDP/8E as well,” c-wizz wrote in a Reddit comment. “There’s a whole 19-inch rack that this is supposed to be mounted in. Maybe I can find some manuals and try to put it all together.”

A view of the LGP-30 found in a German basement.
Enlarge / A view of the LGP-30 found in a German basement.

Although the PDP-8/e machines are rare and valuable on their own, the LGP-30 arguably stands out as the most interesting part of the underground discovery as it is part of hacker legend. In the epic “Mel’s Story”, first published on a Usenet newsgroup in 1983, a Librascope programmer named Melvin Kaye was tasked with porting a Blackjack program from the LGP-30 to another computer. Story writer Ed Nather is then tasked with finding a bug in the software, and along the way, he discovers Kaye’s ingenious and unconventional programming tricks. Also, Edward Lorenz is said to have developed chaos theory (and the “butterfly effect”) as a result of meteorological experiments conducted on the LGP-30.

So what was this legendary machine doing in the grandparents’ basement? Ars contacted c-wizz but did not receive a response until this story was published. In a comment on Reddit, c-wizz wrote: “The only thing I know is that my grandfather used it for civil engineering calculations in the 60s and he was one of the few people in the country to own such a computer in a private capacity.

Whatever the grandparent’s reason for using the LGP-30, it seems there might be a relationship between it and the PDP-8/e units found nearby. In another comment, c-wizz wrote: “There appear to be instructions on how to transfer code written for the LGP-30 to the PDP8\e.”

After sitting in a basement for decades, the LGP-30 will likely need some major work to get it up and running again. This is where a qualified computer museum could come in, and c-wizz seems to be interested in it. “It would be really awesome if someone could get this thing working again,” c-wizz wrote. “I found a museum in Germany (where I’m from) that apparently has a working LGP-30. I think I’ll contact them.”

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