[Simh] Tape conversion issues

[Timothe Litt]

On 03-May-15 00:14, Cory Smelosky wrote:
> Hey,
>
> I've converted a tape with `tapedd` and it's in simh format.
>
> However...it seems the record size is not what it wants :(
>
> record length 2448, expected 2720 is output by t10backup, and BACKUP
> under TOPS-10 says it's non-backup-format.  I have confirmed the
> source system can read the tape.
>
> Anyone converted tapes like this before?  I got a pointer on
> conversion earlier, but I was a bit confused by the answer...figured
> I'd ask a wider audience (including someone who has archived a lot of
> tapes that lurks here).
>
>
When asking a question like this, it sure would help if you included the
basic information required to answer it.

What is the source system?  What hardware and software wrote it?  What
commands read the tape "on the source system"?

You can try DIRECT under TOPS-10, as it knows how to recognize a number
of tape formats.

.direct /s/marks mta0:

That said:

t10backup has a number of issues (as it turns out, I'm in the middle of
writing a replacement). 

Here's a guess:

A standard tops-10 backup tape does indeed have a blocksize of 2720 on
9-track tape in core dump format = (32 word header + 512 word page) * 5
frames/word.

2448 sounds like it was written in the rarely-used high-density mode,
which is 4.5 frames/word. This was supported by the DX20, but is not
emulated by simh.  The DX20 was not supported on the KS.

TOPS-10 didn't support this mode, but you might have a TOPS-20
interchange tape (backup-compatible) that was written on it.  Trivia:
this is a rare case where TOPS-20 supports a hardware feature that
TOPS-10 does not.

If I have time later today, I'll write a conversion utility to convert a
tape image from high-density to core dump mode.  I suspect this will
solve your problem - but in any case, it should be generally useful.

Can you provide a (preferably small) sample tape so that I can verify
this analysis?



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