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From: pec@necntc.NEC.COM (Paul Cohen)
Newsgroups: comp.arch
Subject: Re: What with these Vector's anyways? [really string ops]
Message-ID: <7967@necntc.NEC.COM>
Date: Tue, 4-Aug-87 09:16:41 EDT
Article-I.D.: necntc.7967
Posted: Tue Aug  4 09:16:41 1987
Date-Received: Thu, 6-Aug-87 01:29:59 EDT
References: <218@astra.necisa.oz> <142700010@tiger.UUCP>
Reply-To: pec@necntc.UUCP (Paul Cohen)
Distribution: world
Organization: NEC Electronics Inc.  Natick, MA 01760
Lines: 46
Keywords: scalar vs. vectors, benchmarks


In article <1699@comp.arch> tim@.amdcad.AMD.COM (Tim Olson) writes:

>Many processors have specialized instructions for strings -- Intel's 80x86
>family (movs, cmps), AT&T's 32100 (strlen, strcmp), National's 32x32
>family (movs, cmps), NEC's V70 (movc, cmpc), Fairchild's Clipper (movc,
>cmpc macros).  However, most of these don't address "C-type" strings;
>they require a character count as a parameter.

With respect to the V70 I feel that I must add a point of clarification.
It is true that the movc and cmpc instructions require a string length
to be specified (they also require you to specify whether to use eight
or sixteen bit characters), but these are not the only character string 
operations that the V70 supports.  There are also:

	CMPCF	(compare character string with filler)
	CMPCS	(compare character string with stopper)
	MOVCF	(move character string with filler)
	MOVCS	(move character string with stopper)
	SCHC	(search for character)
	SKPC	(search for not a character)

each of which has eight and sixteen bit versions.  Of these
instructions, CMPCS and MOVCS support C language strings and in fact 
strings terminated by any character you want to specify.  In addition,
SCHC can be used as a string-length operation by C.

The V70's character string move instructions also allow you to specify 
whether to move the string in a forward or backward direction, a critical 
issue when source and destination overlap.  

The V70 also has a complement of bit-string operations; specifically
there are:

	MOVBS 			NOTBS
	ANDBS			ANDNBS
	ORBS			ORNBS
	XORBS			XORNBS
	SCH0BS			SCH1BS		(search for ...)

each of which can be specified to work in a forward or reverse
direction.

In performing string operations, whether bit, byte or half-word, the V70 
reads and writes memory 32-bits at a time.   Can anyone comment on this
with respect to the other 32-bit micros?