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In article <240@ssp1.idca.tds.philips.nl> dolf@idca.tds.PHILIPS.nl (Dolf Grunbauer) writes:
>Just a short I-just-want-to-know question: is it true that the DEC-10 systems
>processors were designed for an efficient Lisp implementation, and was it 
>efficient ?

Yes, the PDP-6 (the immediate predecessor to the PDP-10) was designed
with Lisp in mind, and for many years the PDP-10 was *the* standard
engine for running Lisp.  There were three major Lisps for the PDP-10;
Stanford Lisp 1.6/UCI Lisp/Rutgers Lisp, BBN/Xerox Interlisp, and MIT
MacLisp.

The Stanford PDP-6 had a machine instruction to implement CONS (this
was in 1964 when DEC would implement custom instructions in an
individual processor for customers) and the Lisp 1.6 sources had
support for it under an assembly switch, but to my knowlege it was
never turned on and the Stanford PDP-10 did not have CONS.

The main benefit for Lisp was the PDP-10's halfword instructions and
indexing, which made it ultra-easy to build lists in an efficient
manner and to chase down these lists.  The main thing that eventually
killed the PDP-10 for Lisp was the address space issue and the absence
of any faster CPU's after 1975.  A 30-bit address space Common Lisp
was developed, but it had no particular advantages over Lisp on other
machines.

A fast PDP-10 could be built today to run Common Lisp quite
competitively, but without any of the display facilities modern
Lispers are used to it wouldn't be interesting.

Mark Crispin / 6158 Lariat Loop NE / Bainbridge Island, WA 98110-2020
mrc@CAC.Washington.EDU / MRC@WSMR-SIMTEL20.Army.Mil / (206) 842-2385
Atheist & Proud / 450cc Rebel pilot -- a step up from 250cc's!!!
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