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From: winkler@apple.UUCP (Dan Winkler)
Newsgroups: net.micro.mac
Subject: Re: Mac Cache
Message-ID: <104@apple.UUCP>
Date: Wed, 30-Jul-86 17:44:39 EDT
Article-I.D.: apple.104
Posted: Wed Jul 30 17:44:39 1986
Date-Received: Thu, 31-Jul-86 07:38:57 EDT
References: <932@hounx.UUCP> <842@wang.UUCP> <2017@calmasd.CALMA.UUCP> <2787@sdcc6.ucsd.EDU>
Reply-To: winkler@apple.UUCP (Dan Winkler)
Organization: Apple Computer Inc., Cupertino, USA
Lines: 16

There has been a lot of confusion regarding the RAM cache on this
network.  I have asked the author of the RAM cache to write a brief
response to some of the most common questions, such as how to make the
RAM cache work with applications which need the second screen, and he
has agreed to do so when his workload permits.  In the meantime, let me
pass on one simple point he made to me which has been repeatedly
misunderstood:

	The RAM cache IS a write through cache!  

It is the file manager which is not strictly write through -- it will
buffer up writes until it has a whole block to flush to the disk.  This
is true for any Mac, whether it's using the RAM cache or not.  This is
of course exactly what you want since there would be a severe
performance penalty associated with doing a physical disk access for
every single byte write.