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From: jms@antares.UUCP (Joe Smith)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Disk Questions for WorkBench replacement project
Summary: Disks have 2 dates
Message-ID: <420@antares.UUCP>
Date: 13 Mar 89 04:28:25 GMT
References: <21173@agate.BERKELEY.EDU> <821@microsoft.UUCP> <6200@columbia.edu>
Reply-To: jms@antares.UUCP (Joe Smith)
Organization: Tymnet QSATS, San Jose CA
Lines: 30

In article <6200@columbia.edu> simon@copper.UUCP (Thor Simon) writes:
>I vaguely recall hearing something in this group earlier during the
>discussion of Project D about some copy-protection schemes looking at
>the time/date stamp on the disk.  Hunh.  I didn't think there was a
>time/date stamp on the format itself.  Maybe I'm wrong, but if not,
>this could be a cheap way out, as that would make it two IDs (name and
>date) rather than one.

AmigaDOS disks have two dates in the root block.  One is updated whenever
anything is written on the disk, the other is set when the disk is formatted
or diskcopied.  The DISKCOPY that comes with Workbench makes a track-for-track
copy of the disk with two exceptions.  1) The name is set to "copy of ..." and
2) the volume creation date is set to the current date/time.  Even if you
you relabel the disk so that it has the same name as the original, Workbench
can tell them apart due to the different volume creation dates.  If you run
a different diskcopy program, one that makes an exact duplicate, then you
should remove the duplicate before exiting the copy program so that
Workbench will not be confused by seeing two disks with the same name and
same creation date in two different drives.

Technical details:

  A block of 512 bytes is treated as 128 words of 32 bits each.  Words 105-107
contain the volume modification date/time.  Words 108-120 have the volume
name.  Words 121-123 contain the volume creation date/time.
-- 
Joe Smith (408)922-6220 | jms@antares.Tymnet.COM or jms@opus.Tymnet.COM
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