12 Dec
2014
12 Dec
'14
10:38 p.m.
On 12/12/2014 09:04 PM, Jon Elson wrote:
OK, that narrows things down QUITE a bit. I worked
with some Exabyte
drives and others that had a lot of constraints on what you could do,
and you could do some interesting things. I think you could write
zero-length blocks, and they would show up just like that when
read. Clearly on 9-track, there SHOULD BE no such thing as a
zero-length block, but I suppose some drives could actually write
such a thing at 1600. A preamble, CRC, LRCC and postamble, with
no data. But, that OUGHT to be an illegal command.
I seem to remember on certain tapes, that very short records are
discarded or reading; something like a "noise" threshold of 7 bytes.
But that could be for 7-track and 800 9-track. I don't recall--but
regardless, mistaking a 0-length record, should one occur, for a
filemark is not catastrophic.
--Chuck