Pertec Tape Drive Interface Musings
cclist at sydex.com
Wed Jun 10 15:52:03 CDT 2015
On 06/10/2015 12:36 PM, Johnny Billquist wrote:
> One problem with "preserving errors" is that actual tapes do not have
> any indication that you have a tape error. In fact, many times you can
> recover a tape block by repeatedly read it. Eventually you might read it
> without errors. Not to mention how many tapes I have "fixed" by just
> folding the tape in the opposite direction where there have been a
> bend/kink in it. Easy fix.
> I guess it could possibly be useful to indicate a bad block on a tape,
> in order to preserve the numbering of all the blocks, and constantly
> giving a read error when used in a simulator. But it's kindof a weird
> reflection of a physical error into a virtual one.
...and some errors are correctable by the formatter (and so indicated on
the interface). I see no way to indicate that in the SIMH tape proposal.
Earlier, I discussed how I've begun appending metadata to tape image
files after the EOM indicator. Thus far, no simulator chokes on it. I
really need to extend it. Right now it just indicates date, device
information, notes from the person doing the reading and error messages
during reading and file structure; e.g.
536 x 10240 bytes
Filemark at block 537
3 x 80 bytes...
Okay for now; save for a photo of the tape. Basically, anything known
before and during reading of the tape and writing of the image.
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