Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!mtxinu!taniwha!paul
From: paul@taniwha.UUCP (Paul Campbell)
Newsgroups: comp.sys.mac.programmer
Subject: Re: XFCN/XCMD string in LSC C v3.0
Message-ID: <347@taniwha.UUCP>
Date: 15 Apr 89 19:48:26 GMT
References: <22027@dhw68k.cts.com> <2786@pegasus.ATT.COM>
Reply-To: paul@taniwha.UUCP (Paul Campbell)
Organization: Taniwha Systems Design, Oakland
Lines: 24

In article <2786@pegasus.ATT.COM> ech@pegasus.ATT.COM (Edward C Horvath) writes:
>
>What SHOULD happen, naturally!  Listen carefully, and re-read as necessary:
>The PC is used to fetch instructions, from the cache if there's a hit, from
>RAM otherwise.  ALL other memory references are to/from the data cache if
>there is one, and all writes to the data cache are write-thru.
>
>This is so simple that it is hard to screw up.

well not quite that simple, the tags in the caches are 'virtual' addresses,
the MacOS (24 bit) aliases the same memory locations with different
addresses (yes .... the Handle tags in the high byte! :-) on the '030
they get away with this in the data cache (it doesn't matter in the
instruction cache because you don't write to it) by setting the WA bit in
the cache control register.

They also have to do an instruction cache invalidate when doing a _LoadSeg.

	Paul

-- 
Paul Campbell
Taniwha Systems Design			UUCP:		..!mtxinu!taniwha!paul 
Oakland CA				AppleLink:	D3213