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From: mks@cbmvax.commodore.com (Michael Sinz)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Correct code for turning off 020/030 caches?
Message-ID: <22294@cbmvax.commodore.com>
Date: 10 Jun 91 12:39:31 GMT
References: <1991Jun5.033401.27422@en.ecn.purdue.edu> <mykes.3186@amiga0.SF-Bay.ORG> <1991Jun8.132157.8194@starnet.uucp>
Reply-To: mks@cbmvax.commodore.com (Michael Sinz)
Organization: Commodore, West Chester, PA
Lines: 58

In article <1991Jun8.132157.8194@starnet.uucp> sschaem@starnet.uucp (Stephan Schaem) writes:
>
>
> Just a qucky to turn cache off:
>Check the CPU with exec	(Execbase, attflags)
>if 2.x or greater use the exec function: CacheControl
>Otherwise try the following...
>
>	move.w	#$4000,($dff09a).l
>	lea	NoCache(pc),a0
>	lea	($80).w,a1
>	move.l	(a1),-(sp)
>	move.l	a0,(a1)
>	trap	#0
>	move.l	(sp)+,(a1)
>	moveq	#0,d0
>	rts
>
>NoCache:
>	movec	CACR,d0
>	and.b	#$fe,d0
>	movec	d0,CACR
>	rte
>

Do *NOT* do this!  It will not work correctly.

Under 2.0 there is a function call for cache control.
But, if you need to do it under pre-2.0 systems,
use the Supervisor call!  The above method will *NOT* work
correctly in all machines and/or all software running.

Example:

	.
	.
	.
	lea	NoCache(pc),a5
	move.l	_AbsExecBase,a6
	jsr	_LVOSupervisor(a6)
	; D0 now has the CACR register in it too...
	.
	.
	.

NoCache:
	movec	CACR,d0
	and.b	#$fe,d0	; This is only right for 68020/030!
	move.c	d0,CACR
	rte

/----------------------------------------------------------------------\
|      /// Michael Sinz  -  Amiga Software Engineer                    |
|     ///                   Operating System Development Group         |
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|\\\///    Programming is like sex:                                    |
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