[Coco] Vcc+DW4 to access real floppy drive on Coco-3 ?

[Gene Heskett]

On Tuesday 08 July 2014 01:33:22 Kandur did opine
And Gene did reply:
> My HD is a Seagate Barracuda ST32550N 2.1 GB SCSI.
> Any suggestions how should I set it up?
> 
> Kandur

In the nitros9 sources, study the superdescriptor docs & code comments. 
There is a bit you can set (with dmode, running dmode in the "file" mode 
by putting a "-" in front of the filename you want it to edit, then 
rebuild the boot disk to use that descriptor) in the drives descriptor 
which controls how format works.

I've forgotten which bit it is now, but the effect of it switches format's 
operation from formatting the whole drive based on its asking the drive 
how big it is, to using the arguments you give it on the command line, and 
only formatting the outer x megabytes. I'd set that bit so as to make it 
use your arguments and give arguments that would be a hair short of 500 
megs so that the cluster size is not driven above 4.  Then when format is 
finished, look at DD_SIZ in LSN0, and set the /sh descriptors wpc and ofs 
values to one more than that figure, again using dmode in the file mode so 
its committed to that descriptor no matter how many times you run the mb 
script.  This then becomes the first vdisk, and can be used either for 
HDBDOS access once HDBDOS has this value edited into it, see the docs, or 
as bootable nitros9 disks.

I don't have any os9 stuffs in the first 4 vdisks as those are the vdisks 
HDBDOS would use when switched to use vdisks (DRIVE0, DRIVE1, DRIVE2 and 
DRIVE3) instead of real floppies.

> Monday, July 7, 2014, 8:46:49 PM, you wrote:
> > On Monday 07 July 2014 23:27:54 Kandur did opine
> > 
> > And Gene did reply:
> >> Thanks Gene.
> >> 
> >> Kandur
> >> 
> >> Monday, July 7, 2014, 11:10:29 AM, you wrote:
> >> > On Monday 07 July 2014 11:59:29 Kandur did opine
> >> > 
> >> > And Gene did reply:
> >> >> Bill, what I wanted was, to access physical floppy drives on the
> >> >> Coco, while running Nitro OS-9 on VCC. Drive ON/OFF don't seem to
> >> >> work on the Coco's physical drives from OS-9.
> >> >> 
> >> >> Kandur
> >> > 
> >> > That is because in nitros9, HDBDOS is not used and there are two
> >> > different descriptor "families".  You configure the bootfile to
> >> > include the proper /D0, /D1, or /D2 for the physical drives, but
> >> > you have to configure /SH to access the virtual drives.  If you
> >> > have the drive space beyond the end of the os9 "partition", then
> >> > /SH, configured correctly, can access any virtual disk, in
> >> > however many groups of 255 that you have room for on the hard
> >> > drive.
> >> > 
> >> > You have to dmode 3 variables in the descriptor to do this.
> >> > 
> >> > The "stp", range $00 to $ff selects the vdisk within the group.
> >> > wpc (1 hex byte) and ofs (hex int) are to be used to point at the
> >> > first sector of each group of 255 virtual disks.  So on my main
> >> > hard drive, /SH is currently set to look at the $80th, or 128th,
> >> > disk in group 0, whose address in wpc=1D and ofs=BB90.  Leave the
> >> > dollar sign out of the dmode command though, its not needed.
> >> > 
> >> > Each additional group is done by adding to the $1D,BB90, the
> >> > number of sectors that 256 disks of 35 track, 18 sectors per
> >> > track that a single sided disk image would occupy.  The next
> >> > group(1) then would have a starting sector of $1DBB90 +
> >> > $27600=$20,3190.
> >> > 
> >> > Repeat, adding $27600 each time until out of drive space. ;-)
> >> > 
> >> > I hope this helps.
> >> > 
> >> > Cheers, Gene Heskett
> > 
> > One thing I perhaps didn't detail well enough, is that the $1DBB90
> > used above, is from my main drive, which has about 500 megs for
> > nitros9, leaving about 500 megs for virtual disks.  Your hard drive
> > quite likely will have a different size recorded in its LSN0 at
> > DD_SIZ.
> > 
> > I have 2 identical 1Gb seagate Hawk scsi-ii drives, the second one is
> > formatted all nitros9.  That goes over the clusters demarcation
> > twice, so while the main drive functions with a 4 sectors per bit in
> > the FAT, the 2nd drive uses one bit in the FAT to represent 16
> > sectors.  Its odd, but a 1 byte file then blocks out 16 sectors for
> > that one byte file.  With a gigabyte to wander around in, its not
> > really a problem as the files size, and the amount of disk it
> > allocates, are two different things.
> > 
> > Cheers, Gene Heskett


Cheers, Gene Heskett
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