[W/K] :: PDP-20

  PDP-20 n. The most famous computer that never was. PDP-10 computers
     running the {TOPS-10 operating system were labeled `DECsystem-10' as
     a way of differentiating them from the PDP-11. Later on, those systems
     running TOPS-20 were labeled `DECSYSTEM-20' (the block capitals being
     the result of a lawsuit brought against DEC by Singer, which once made a
     computer called `system-10'), but contrary to popular lore there was
     never a `PDP-20'; the only difference between a 10 and a 20 was the
     operating system and the color of the paint. Most (but not all) machines
     sold to run TOPS-10 were painted `Basil Blue', whereas most TOPS-20
     machines were painted `Chinese Red' (often mistakenly called orange).
  
  

  PDP-20
       
          The most famous computer that never was.  PDP-10 computers
          running the TOPS-10 operating system were labelled
          "DECsystem-10" as a way of differentiating them from the
          PDP-11.  Later on, those systems running TOPS-20 were
          labelled "DECSYSTEM-20" (the block capitals being the result
          of a lawsuit brought against DEC by Singer, which once made a
          computer called "system-10"), but contrary to popular lore
          there was never a "PDP-20"; the only difference between a 10
          and a 20 was the operating system and the colour of the
          paint.  Most (but not all) machines sold to run TOPS-10 were
          painted "Basil Blue", whereas most TOPS-20 machines were
          painted "Chinese Red" (often mistakenly called orange).
       
          [{Jargon File]
       
          (1994-12-21)