15 Dec
2014
15 Dec
'14
5:23 a.m.
Two tape marks is just a convention used by some
software to indicate
the logical EOT. It has no special meaning for the hardware.
Perhaps on some drives (such as 9-tracks). But I did run into one
drive, one of the relatively modern cartridge drives with tapes about
the size of a TK50, which had a relatively elaborate encoding scheme in
which EOT was different from two consecutive tapemarks, but it mapped
between the two in each direction and the drive refused to even try to
read past EOT. In order to recover data that had been written over,
the recommended procedure was to write enough to overwrite the EOT mark
and then power down the drive while it was writing more. (Recommended
by users, not the maker IIRC.)
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