Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!decwrl!hplabs!hp-sdd!ucsdhub!sdcsvax!net1!hutch
From: hutch@net1.ucsd.edu (Jim Hutchison)
Newsgroups: comp.arch
Subject: Chaining routines, sequencers (query)
Message-ID: <4981@sdcsvax.UCSD.EDU>
Date: 27 May 88 07:44:24 GMT
Sender: nobody@sdcsvax.UCSD.EDU
Reply-To: hutch@net1.UUCP (Jim Hutchison)
Lines: 40

<>
I am interested in finding out about techniques for dynamicly chaining
routines together in microcoded hardware.  Currently I am using a AMD2910
based VLIW style function processor (cheeky name) and am doing co-routines
via "jump vector" operations.  This works fine for pairs of routines, but
when I suddenly want more than just an input and an output operation...

The overhead for the linked pair is 1 instruction per "call", which can
usually be hidden behind a main memory reference.  Has anyone got a fancy
do-dad which can set up a stack to roll down?  At each call, call the
routine one farther down in the stack.  Like this:

	setup()
		push routine A
		push routine C
		push routine B
		push routine Reset Pointer
	A()
		do stuff
		call next	; co-call next filter
	B()
		do stuff
		call next	; co-call next filter

	C()
		do stuff
		call next	; co-call next filter

	Reset Pointer()
		vector stack = top

An added convenience would be that it would reset to top of stack on bottom
out, but it is not necessary.  Why do it in software at all?  Things have
to be maleable, new filters as needed or dreamt up and sold. :-)

Suggestions?  Related hardware?  Any DSP chips that allow this?

    Jim Hutchison   		UUCP:	{dcdwest,ucbvax}!cs!net1!hutch
		    		ARPA:	Hutch@net1.ucsd.edu
Disclaimer:  The cat agreed that it would be o.k. to say these things.