*BSD News Article 58614


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Newsgroups: comp.unix.bsd.freebsd.misc
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From: mark@seeware.DIALix.oz.au (Mark Hannon)
Subject: Re: ???---RAM vs cache : is 256k cache enough for 24M RAM ---???
Organization: SeeWare Software
Message-ID: <DKFJoD.EIq@seeware.DIALix.oz.au>
References: <4bc3g4$eo@docder.demon.co.uk> <4brk1q$dt8@hustle.rahul.net>
Date: Sun, 31 Dec 1995 02:45:49 GMT
Lines: 43

Bill Hogan (bhogan@rahul.net) wrote:
: dmitri (100334.712@compuserve.com) wrote:

: : I've got 486DX-2,66 computer with 8M RAM, 256k cache and thinking to add 8 or
: : 16 M more. The motherboard is not upgradable to more cache. As I heard too much
: : RAM can slow down system without adding cache. What is the ratio RAM vs. cache?

: : Thank you.

: : ----
: : Dmitri

:   If you have 256kn sram cache, your mb should I think be able to cache 
: RAM addresses as high as 32mb.

:   128K sram cache is only good up to 16MB ram.

:   The moment you go past 16mb ram, you have to increase your cache because
: otherwise the ram > 16mb will simply be not cached.

:   I have 20MB RAM and only 128kb cache, so I enable the "limit RAM to
: 16MB" option when I compile the Linux kernel. 

Hi all,

Saw this in a linux newsgroup.  Is this a general motherboard problem or
is it only some types of 486 motherboards??  Has anybody done any tests
to see if RAM over 20MB really slows things down?  I am using a 486 DX33
with 20MB RAM and 128KB cache and things are reasonably snappy (I had
8MB before and it's much faster than this!)

Is there anyway I can test/measure the difference between 16MB and 20MB?
ie can I stop the kernel from using >16MB?  If I do this can I use the
4MB for anything useful?

Regards, Mark


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