[Simh] Overwrite last track and set badblocks

[Mark Pizzolato]

On Friday, January 22, 2016 at 7:34 AM, Paul Koning wrote:
> > On Jan 22, 2016, at 10:29 AM, Will Senn <will.senn at gmail.com> wrote:
> >
> > ...
> > OK. I figured some of this out...
> >
> > In RT-11v5.3 if I have the following ini section for a disk:
> > set rl1 writeenabled
> > attach rl1 storage.dsk
> >
> > And I say no initially to the prompt:
> > Overwrite last track? [N]N
> >
> > When I try to initialize the disk in RT-11, I get an error:
> > .initialize dl1:
> > DL1:/Initialize; Are you sure? Y
> > ?DUP-F-Bad block in system area DL1:
> >
> > But, if I answer Y:
> > Overwrite last track? [N]Y
> >
> > All is good in the world. I get no errors initializing and I no longer get
> prompted at startup:
> > .initialize dl1:
> > DL1:/Initialize; Are you sure? Y
> >
> > .dir vol:
> >
> > 0 Files, 0 Blocks
> > 10172 Free blocks
> 
> That all makes sense.  Since you were initialing an RL01 or RL02, the system
> expects a DEC Std 144 bad block table.  In the first try, it wasn't there.  What
> may have happened is that initialize used what it found and mistook it for
> valid, and ended up believing it was told that block 0 is bad.  That would
> certainly make initialize unhappy.
> 
> > This being the case, it appears that set badblock does not appear to be
> required. For the sake of discussion, if there is a case when it is required, is it
> a one-shot deal where the command is run in simh and then left out of the
> ini file after the bad block is created?
> 
> The bad block table lives on the disk, i.e., in the disk image file.  Unless it's
> overwritten, or you recreate the file, it will persist.  So yes, it is a one-shot
> deal.

>From the wording of Will's question, it is not 100% clear that he's really asking
if executing a "SET RL0 BADBLOCKS" as a command is ever required.  The 
answer to this question is NO since the question will automatically be asked 
when the disk image is initially created.  

If someone really wanted to preserve a previously created, but probably 
empty disk image file and add a DEC144 bad block table to the last track of 
the disk the "SET RL0 BADBLOCK" command would do that.  A sequence 
like this might be useful:

     sim> ATTACH RL0 test.dsk
     RL: creating new file
     Overwrite last track? [N]
     sim> SET RL0 BADBLOCK
     Overwrite last track? [N]y
     sim> 

- Mark