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Tag on track 41 of some floppy-disks

per

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Jan 21, 2008
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I am going through and once and for all properly archiving my collection of floppy disks, and from time to other I come across 48tpi disks with a peculiar 128-byte FM-modulated tag on head 0 of the 41st cylinder. Sometimes it is also accompanied by empty tags on head 1 and both heads of the 42nd cylinder as well, which you can see in the attached screen capture.

This got me curious. Are any of you familiar what this was used for? My guess is that one particular type of master-disk copier would add such a tag as a signature, but I see quite similar tags on different disks from different software companies. I also see that sometimes, if there are many disks in a software product and there are tags like this, not all of the disks may have the tags.
 

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krebizfan

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May 23, 2009
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I think that was done by the mass formatter and the extra track would have data that indicated a disk that failed letting a different machine kick out the failures. I thought I read a list of a couple variations on what was stored in the extra track but I can't find it anymore.
 
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