General TC11 DECtape diagnostic/formatter questions

Josh Dersch derschjo at
Tue Nov 8 21:19:35 CST 2016

On 11/8/16 1:43 PM, Noel Chiappa wrote:

>      > From: Josh Dersch
>      > If I run them on SIMH configured as an 11/44, I see the same behavior.
>      > If I run them on SIMH configured as an 11/20, then I get the printout
>      > described in the documentation and listings. ... I haven't yet dug in
>      > to see what accounts for the difference -- any ideas?
> The fact that the simulator produces identical results to the real hardware
> would argue that it's not a bug in that particular hardware. So it must be
> some real difference between the two.
> There are subtle differences between the 11/20, and other 11's - e.g. on the
> /20 SWAB does't clear the V bit - maybe it's one of them? It might be worth
> trying setting the CPU type to other values, and see if it works on any other
> machine type.
Turns out it's the XXDP XM monitor causing the issues (I would wager 
that it sets up the MMU in such a way that older diagnostics don't deal 
well).  If I run it under the SM Monitor it works.  Whew :).

>      > 2) I'm looking for means to format DECtapes on the TC11. ... The
>      > maintenance manual only indicates "a special program supplied with the
>      > TC11 system," and I haven't managed to find it.
> The UNIX V6 distro includes a standalone program, tcf.s, to format DECtapes.
> I don't know if you have a running V6 system (real or emulated) to assemble
> it one; if you want me to assemble it and provide it as binary (in a variety
> of formats, e.g. .LDA format), let me know.

I could probably get a V6 distribution running if I need to, but if you 
have the means to do so easily, that would be handy so I can at least 
have another tool to try out.  Something that XXDP can load would be useful.


> 	Noel

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