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From: geoff@desint.UUCP (Geoff Kuenning)
Newsgroups: net.micro.68k
Subject: Re: detecting processor type (68000/68010/etc) in software?
Message-ID: <174@desint.UUCP>
Date: Sun, 28-Oct-84 16:14:12 EST
Article-I.D.: desint.174
Posted: Sun Oct 28 16:14:12 1984
Date-Received: Tue, 30-Oct-84 00:46:42 EST
References: <368@foros1.UUCP> <1753@sun.uucp> <217@rlgvax.UUCP>
Organization: his home computer, Thousand Oaks, CA
Lines: 19

In article <217@rlgvax.UUCP> guy@rlgvax.UUCP (Guy Harris) writes:

>I seem to remember some discussion a while ago on the fastest way to do
>a block move, which implied that the MOVE.L/DBcc pair was faster on the
>68010, but not on the 68000.  (Not that the library routine should burn
>up a goodly number of the cycles saved by trying to do an RTD and catching
>the illegal instruction trap...)

Actually, on both the 68000 and the 68010 a series of MOVEM instructions
beats a DBRA loop all hollow.  This is because the MOVEM instruction makes
use of the processor's instruction prefetch buffer to speed up the
operation.  (This is the reason the 68K makes one extra fetch at the end of
a MOVEM into the registers, a source of chagrin to anyone who MOVEM's too
close to the end of accessible memory!).
-- 

	Geoff Kuenning
	First Systems Corporation
	...!ihnp4!trwrb!desint!geoff