Source : Free On-Line Dictionary of Computing

Johnniac
     
         A {mainframe} computer based on a design by {John
        von Neuman} built at the {Institute for Advanced Study}, USA.
        The Johnniac went live in 1953 and was decommissioned in 1966.
        It's memory consisted of 80 special "Selectron}" {vacuum
        tubes}, each of which held 256 bits of data.
     
        (2003-06-07)