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From: apratt@atari.UUCP (Allan Pratt)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: Big logical sectors and their effects
Message-ID: <2785@atari.UUCP>
Date: 17 Dec 90 22:55:15 GMT
References: <1990Dec13.141210.26853@wam.umd.edu> <3387@medusainformatik.uni-erlangen.de>
Organization: Atari Corp., Sunnyvale CA
Lines: 29

csbrod@medusainformatik.uni-erlangen.de (Claus Brod ) writes:
>Large sectors probably won't hurt performance. ...
>Many disk editors don't know about big 
>logical sectors yet but are being adapted. Application software
>doesn't need to know about things like this and therefore runs
>unaffected.

What he said.

There is another side-effect to large sectors, however: your disk cache
must consist of sector buffers which are as big as the largest logical
sector in your system.  Our hard-disk driver and cache program handle
that case perfectly: the cache program (CACHENNN.PRG) interrogates the
driver, asking "what's the largest logical sector size in the system?"
and it sizes cache sectors accordingly.  Other cache programs probably
do not handle this: they probably assume 512 bytes per sector.

As for clusters, clusters are always 2 sectors long.  This is due to a
bug in GEMDOS.  (The bug is interesting: it says, in effect, "if this
isn't the first sector of the cluster, then it's the last."  Hence, two
sectors per cluster.)  It's possible to fix the bug, of course, but a
disk with clusters larger than two sectors could not be used on a
system with older ROMs, and since large logical sectors fix the same
problem in a way that doesn't rely on having new ROMs, we decided to do
it that way.

============================================
Opinions expressed above do not necessarily	-- Allan Pratt, Atari Corp.
reflect those of Atari Corp. or anyone else.	  ...ames!atari!apratt