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From: blochowi@rt4.cs.wisc.edu (Jason Blochowiak)
Newsgroups: comp.sys.apple
Subject: Re: Hard Disk Construction
Message-ID: <3835@puff.cs.wisc.edu>
Date: 22 Nov 89 20:06:38 GMT
References: <7484.infoapple.net@pro-generic>
Sender: news@puff.cs.wisc.edu
Reply-To: blochowi@rt4.cs.wisc.edu (Jason Blochowiak)
Organization: U of Wisconsin CS Dept
Lines: 28

In article <7484.infoapple.net@pro-generic> ericmcg@pro-generic.cts.com (Eric Mcgillicuddy) writes:
>In-Reply-To: message from jabernathy@pro-houston.cts.com
>One method might be to increase the block size to 1k bytes (4 sectors) since
>Prodos is a block structured OS (right jargon?) this should double the
>effective size to 64Meg. The volume bit map just tracks blocks, not sectors, I
>think. This will increase wastage if you have a lot of small files, but you
>did ask for ANY solution.

	If that were workable, it would indeed expand the max volume size
to 64Mb. However, every ProDOS 8 application (not to mention ProDOS 8 itself)
expects the blocks to be 512 bytes, and therefore sets up buffers, etc., for
block access as 512 byte chunks. The obvious solution would then be to only
run programs that don't do block-level access (most programs only do file-level
access). Well, that still wouldn't quite work out, as when you open a file
under P8, you have to give it a buffer, which (if memory serves) is 1k in size.
This buffer is used for block i/o, and I would imagine that one half is used
for data blocks, and the other is used for index blocks. In any case, if you
doubled the block size, you'd have to double the i/o buffer space, which means
that you'd have to change all the applications... This would probably not be
acceptable to anyone who's not a masochist.

	Btw, you are correct that the volume bit map deals with blocks, not
sectors. The mapping of blocks to whatever unit is appropriate for the device
in question (sectors, in the case of 5.25" disks) is the responsibility of
a device driver.
--
      Jason Blochowiak - blochowi@garfield.cs.wisc.edu or jason@madnix.uucp
       "Education, like neurosis, begins at home." - Milton R. Sapirstein