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From: ejb@think.com (Erik Bailey)
Newsgroups: comp.sys.mac.system
Subject: Re: Some System 7 questions...
Message-ID: <1991May31.164455.13023@Think.COM>
Date: 31 May 91 16:44:55 GMT
References: <1991May31.151901.10137@Think.COM> <1991May31.155150.5074@hubcap.clemson.edu>
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Organization: Thinking Machines Corporation, Cambridge MA, USA
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In article <1991May31.155150.5074@hubcap.clemson.edu> jcocon@hubcap.clemson.edu (james c oconnor) writes:
>[much deleted]
>
>> 3) Why won't the system use the pretty floppy disk icon when I'm in 8-bit
>>    mode?  It persists in using the 1-bit icon.  Incidentally, for you IIsi
>>    owners out there, I *highly* recommend the tip circulation about setting
>>    the RAM cache to 768k -- it at least doubles video performance!
>
>Did Apple change the caching algorithm?  If not, why the huge cache?
>I'd heard that the cache was pretty much a waste of RAM if it got over
>some small number, say 128k (remember when that was how much RAM Macs
>came with?  I owned one of those).
>
>Inquiring minds want to know.
>
>Jim

No, it actually has nothing to do with the disk cache at all!  It's
actually about the memory layout.  NB -- this was NOT my idea, and I've
lost the original post, so this is from memory (pun intended).

Anyway, what happens is that the low (or is it high?) 1meg of memory is
used for video ram.  When small programs are loaded, they get loaded
entirely or partly into this 1meg.  For reasons I don't understand, this
is VERY SLOW memory, possibly because of the frequent video access (?).

Increasing the disk cache to 768k fills up the rest of the RAM (assuming
you have built-in video set to 256 colors, which is 256k).  I guess any
technique that used up this memory in a productive way (eg RAMdisk) would
also work.

Important note -- I have noticed NO speed gain of the 768k cache as opposed
to my old 256k cache in terms of DISK performance.  This is purely a *video*
enhancement.  However, it makes 256-color mode fast enough that I leave my
system there instead of in 16-color mode, since I like the pretty system
7 icons! :-)

--Erik

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