PDP-10 n.
[Programmed Data Processor model 10] The machine that made
timesharing real. It looms large in hacker folklore because of
its adoption in the mid-1970s by many university computing
facilities and research labs, including the MIT AI Lab, Stanford,
and CMU. Some aspects of the instruction set (most notably the
bit-field instructions) are still considered unsurpassed. The 10
was eventually eclipsed by the VAX machines (descendants of the
PDP-11) when DEC recognized that the 10
and VAX product lines were competing with each other and decided
to concentrate its software development effort on the more
profitable VAX. The machine was finally dropped from DEC's line
in 1983, following the failure of the Jupiter Project at DEC to
build a viable new model. (Some attempts by other companies to
market clones came to nothing; see Foonly and Mars.)
This event spelled the doom of ITS and
the technical cultures that had spawned the original Jargon File,
but by mid-1991 it had become something of a badge of honorable
old-timerhood among hackers to have cut one's teeth on a PDP-10.
See TOPS-10, ITS, BLT, DDT, DPB, EXCH, HAKMEM, LDB, pop, push. See also http://www.inwap.com/pdp10/.
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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).
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