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From: 6106264@pucc.Princeton.EDU (Paul Licameli)
Newsgroups: comp.lang.forth
Subject: FORTH processors
Message-ID: <3832@pucc.Princeton.EDU>
Date: Fri, 13-Nov-87 02:17:07 EST
Article-I.D.: pucc.3832
Posted: Fri Nov 13 02:17:07 1987
Date-Received: Sun, 15-Nov-87 07:00:46 EST
Reply-To: 6106264@pucc.Princeton.EDU
Organization: Princeton University, NJ
Lines: 41
Disclaimer: Author bears full responsibility for contents of this article


To the gentleman who posted a few days ago with an info request, sorry, I
lost your address and have to make this public.
 
The 1986 FORML conference proceedings has several articles from a team at
Johns Hopkins who designed an experimental (not commercial) FORTH chip.
To wit:
 
Robert Williams, Martin Fraeman, John Hayes, Thomas Zaremba.  _The
Development of a VLSI Forth Microprocessor._  On p. 189.  They discuss
technical aspects of the design and realization (choice of silicon-on-sapphire
for space-based work, use of chip real estate, etc).
 
Same authors.  _A 32 Bit Processor Architecture for Direct Execution of
Forth._  p. 197. The interesting part, instruction set details.
 
Hayes, John.  _An Interpreter and Object Code optimizer for a 32 Bit Forth
Chip._  p. 211.  Shortcuts, like in the cmFORTH assembler:  crunch primitives
where possible, expand low-level cliches in-line; also replacing calls with
branches to avoid unnecessary tail recursion and stack violations.
 
Having read these articles and Ting's _Footsteps in an Empty Valley,_ I can't
help but notice similarities in the chip designs.  For example, there are two
on-chip stack caches, externally microcoded instructions (more bit fields
available than on the 16-bit Novix), ability to combine stackops with
arithmetic, and the single-cycle call, distinguished -- you guessed it! --
by setting the MSB of the instruction to a 0.  Nowhere do I see any credit to
Chuck Himself, but I do see a reference in the third article, dated 1984:
Ballard, B.  "FORTH Direct Execution Processors in the Hopkins Ultraviolet
Telescope," _Journal of Forth Applications and Research,_ 2,1 1984, pp. 34-37.
Are these old ideas?  Or are these similarities inescapable features necessary
for any worthy Forth processor, the real ingenuity lying in the invention of
Forth itself?  One wonders.
 
Oh, I almost forgot:  the name of the beast was JHU/APL 32, if that means
anything to you.
 
Please mail me your final results if you don't post.  I saw your BYTE article;
could you mail me some info about the WISC machine et al?
 
Paul R. Licameli