Path: utzoo!attcan!uunet!mailrus!iuvax!maytag!watstat!dmurdoch
From: dmurdoch@watstat.uwaterloo.ca (Duncan Murdoch)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Cache and Ram Disk
Message-ID: <1990Jun15.201058.22272@maytag.waterloo.edu>
Date: 15 Jun 90 20:10:58 GMT
References: <13910.2678b7ff@maven.u.washington.edu>
Sender: daemon@maytag.waterloo.edu (Admin)
Organization: University of Waterloo
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In article <13910.2678b7ff@maven.u.washington.edu> klliou@maven.u.washington.edu writes:
>I have just increased 2 MB memory for my AT.  I want to use it for cache and
>ram disk.  Of course I hope it can be used fully.  How much of it should be
>assigned to cache? or ram disk?  Is there any PD tool that can be used to
>test the performance for different combinations?
>
>Any help will be appeciated.

I've found a cache more useful than a ramdisk.  A ramdisk is most useful when
you want fast writes as well as reads (most caches let writes pass through, 
for safety), but in my experience, temporary files that I'd like to put
on a ramdisk soon grow too large, and I end up with them on a real disk
anyways.  If I had your 2 MB, I'd put 1 meg as a cache, and configure the
other meg as expanded (EMS) memory.  If you don't have any programs that
know about EMS, you might consider a 1 MB ramdisk, but I think you'll find it
hard to make good use of it.

BTW, if you want to monitor cache usage, I wrote a program called CACHEMON,
available on Simtel20 as CACHEMON.ZIP, that will give a report of how many
logical read and write requests there have been, and how many made it past
the cache as physical read and write requests.  With a 1 Meg cache, I typically
see all but about 18% of read requests being satisfied from the cache.

Duncan Murdoch