[Coco] NitrOS9 and B&B XT-RTC

[Gene Heskett]

On Monday 17 June 2013 21:43:01 Bob Devries did opine:

> Hi Mark,
> 
> That's a very good write-up of the HDB-DOS/SuperIDE boot creation.
> Thanks.
> 
> One question, though: Is it possible to access the HDB-DOS (DECB)
> virtual disks from within NitrOS9? I guess what I'm saying is: Can I
> read/write the "boot" disk in slot 255 from NitrOS9 with a view to
> making small(ish) modifications?
> 
> Regards, Bob Devries
> Dalby, QLD, Australia
> 
Sure Bob, piece of cake, its just another floppy ONCE you have it setup.  
To set it up, use the sh.dd descriptor.

First, do a ded /dd@ to look at LSN0 of the hard drive.  You want to write 
down the DD.SIZ value, its in hex.  Quit dEd, you're done with it for now. 
Then locate the copy of sh.dd in the modules/rbf tree of the distribution.  
Get ready to run

dmode -sh.dd stp=FF wpc=(the first 2 hex chars of DD.SIZ) ofs=(the last 4 
characters of DD.SIZ + 1)

Make a boot disk using that descriptor, reboot to it, and do a dir /sh, and 
you should be looking at disk 255 (the stp=$FF) of the HDBDOS 'partition'.

To summerize, the wpc and ofs settings should be the DD.SIZ of the os9 
formatted section of your hard drive.

Then, the stp=value is which of those HDBDOS disks it points at.  Setting 
stp=00 should show you the first disk, which starts on the next sector of 
the hard drive beyond the DD.SIZ in the hard drives LSN0, $01 and its 
drive1, $02 and its drive2 to rsbasic etc.
HDBDOS virtual disks are fixed size, same as the original 35 track coco 
disks.  The driver adds 630 to the wpc & ofs values for every increment of 
the stp value.

I hope this helps.

Cheers, Gene
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