I80386 String Operations

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Article #1635

#1635

From: Mark Campbell
Date: Mon, 20 Jul 1987 13:59

21 lines
1291 bytes

Could someone out there explain or point to literature explaining the I80386
string manipulation operations?  What I'm wondering is why the I80386 string
operations are so efficient.  For example, the sequence*

		slodb
		scab

in a string compare loop appears to be much faster than the corresponding
MC68020 load and compare instructions, even if the MC68020 can access memory
more quickly in all (byte, word, and longword) normal cases.

The only theory I have is that these instructions are somehow using the
memory bus more efficiently than you would think, given that they are byte
operations.

Thanks.

* INTERACTIVE I80386 assembler
-- 
						Mark Campbell
						{}!ncsu!ncrcae!sauron!campbell

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Path: arc1-ca.pugleaf.net!utzoo!mnetor!uunet!seismo!gatech!ncsuvx!ece-csc!ncrcae!sauron!campbell
From: campbell@sauron.Columbia.NCR.COM (Mark Campbell)
Newsgroups: comp.sys.intel
Subject: I80386 String Operations
Message-ID: <917@sauron.Columbia.NCR.COM>
Date: Mon, 20-Jul-87 09:59:56 EDT
Article-I.D.: sauron.917
Posted: Mon Jul 20 09:59:56 1987
Date-Received: Tue, 21-Jul-87 04:57:49 EDT
Organization: Advanced Systems Development, NCR Corp., Columbia, SC
Lines: 21
Keywords: Performance, I80386, Strings, Characters