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From: ix21@sdcc6.ucsd.EDU (David Whiteman)
Newsgroups: net.micro.mac
Subject: Re: Mac Cache
Message-ID: <2787@sdcc6.ucsd.EDU>
Date: Wed, 30-Jul-86 02:47:14 EDT
Article-I.D.: sdcc6.2787
Posted: Wed Jul 30 02:47:14 1986
Date-Received: Thu, 31-Jul-86 02:49:10 EDT
References: <932@hounx.UUCP> <842@wang.UUCP> <2017@calmasd.CALMA.UUCP>
Reply-To: ix21@sdcc6.UUCP (David Whiteman)
Organization: U.C. San Diego, Academic Computer Center
Lines: 26

In article <2017@calmasd.CALMA.UUCP> cjn@calmasd.UUCP (Cheryl Nemeth) writes:
>Does the cache do an automatic write-through all the time?  It seems like
>it would be very dangerous to use if it doesn't.

There is an Apple representative who speaks at our users group
frequently.  He once told us the cache is NOT write-through;
although there are ways to flush the cache under programmer's
control.  There were also taken to insure data is not loss despite
the lack of an automatic write-through.  Apparently there is a cache
bit which can be set for an application.  If the application cache
bit is set this means that the application's resources can be cached
without problem.  If the cache bit is not set caching still occurs,
but only resources in the system file and perhaps the finder are
cached.  I did not understand whether the cache becomes automatic
write-through if the cache bit is unset or not, or whether an
application is just not suppose to change system resources.  Also
only resources are cached, and caching is primarily suppose to
reduce time in relauching applications and relauching the finder.

I don't know how true the above is.  The Apple rep has a tendency to
over simplify things.
-- 
David Whiteman,
University of California, San Diego 

The America Cup, don't leave Perth without it.