2 definitions
for PDP-20
From Jargon File (4.3.1, 29 Jun 2001) :
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).
From The Free On-line Dictionary of Computing (27 SEP 03) :
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)