[Simh] Tape conversion issues

[Cory Smelosky]

On Sun, 3 May 2015, Timothe Litt wrote:

> When asking a question like this, it sure would help if you included the
> basic information required to answer it.
>

Yeah, that would help.  Sorry, was running around doing a bunch of things 
when I sent that off.

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

An SC-40 with a DLT-7000 tape drive hanging off it, using a (Probably 
heavily modified) TOPS-10.

.ASSIGN MZA50: TAPE:
.RUN BACKUP
/TAPE TAPE:
/SSNAME KDK
/SAVE KDK:

> You can try DIRECT under TOPS-10, as it knows how to recognize a number
> of tape formats.
>
> .direct /s/marks mta0:
>

Thanks, will try that.

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

Ahhh.

> 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.
>

Yeah, which this seems to not be. ;)

> 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.
>

Hmmmm.  I wonder why the SC-40 running this TOPS-10 build is using 
high-density mode then?

I've heard that there's some sort of command to change the tape format, 
any ideas?

(I can rewrite the tape, I wrote the tape giving me issues yesterday 
afternoon)

> 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.
>

Thanks, yes - that should help.

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

Sadly, it's >300M (explains the high-density mode, now that I think about 
it) and I must control its spread so I'll send it to you off-list.

>
>
>

-- 
Cory Smelosky
http://gewt.net Personal stuff
http://gimme-sympathy.org Projects