Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!uxm.sm.ucl.ac.UK!andrew
From: andrew@uxm.sm.ucl.ac.UK (Andrew Dawson)
Newsgroups: comp.sys.atari.st
Subject: 2K of disk space lost?
Message-ID: <8903211617.AA27122@uk.ac.ucl.sm.uxm>
Date: 21 Mar 89 16:17:58 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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If I format a disk double sided from the desktop, it will have 80
tracks of 9 sectors. One of these is the boot sector, and there are 2
copies of the Fat Allocation Table (5 sectors each) and a root
directory (7 sectors).

Now, 2*80*9-1-2*5-7 = 1422, and at 512 bytes per sector this is
728064 bytes. However, after formatting is complete (assuming no bad
sectors), I am told that the disk has 726016 bytes free. 2K is
unaccounted for.

Also, if I format a 720K disk on an MS-DOS machine, DOS reports 730112
bytes free (a FAT is only 3 sectors under DOS). If I take this same blank
disk and put it in my ST, a "show info" reports 728064 bytes free - another
error of 2048 bytes.

A Dfree() call on a TOS formatted disk suggests that the disk has 711
clusters of which 709 are free (yet again suggesting that 2K has been
used). I know that cluster numbers start at 2, but this isn't "used"
space.

Is this a TOS bug, or have I missed something? Anyone got any ideas?



Andrew Dawson
School Of Medicine Computer Unit
University College London