[Coco] VI and VIRQ

[Gene Heskett]

On Wednesday 14 May 2008, Robert Gault wrote:
>Mark Marlette wrote:
>> Gene,
>>
>> offset, virtual drive, etc.....Boisy is the expert on this feature...
>>
>> Mark
>
>I'm not sure what software comes from Cloud-9, but here is what I do on
>my KenTon scsi system.
>
>The only difference between the OS-9 section of an RGBDOS/HDBDOS hard
>drive and the Disk Basic section is the offset added to the LSN#. For
>most people, that offset is constant and stored in the DOS ROM.
>To be able to read an OS-9 disk stored in the Disk Basic section of the
>hard drive, boot disk or otherwise, a new driver is needed that adds the
>Disk Basic + drive number offset to all LSN values.
>
>In fact, I have made such a driver available in my RGBDOS for emulators
>package. If you have the source code for the driver you are currently
>using, it should be easy to modify it to add the required offset value.
>The biggest problem is deciding whether to permit access to all drive
>numbers or just the boot drive. I chose to permit access to any drive
>number so used a byte in the descriptor to store that value, changeable
>using dmode.
>
I've built a floppy boot on a 40 track DS disc, that contains the sh_tc3.dd 
descriptor, and I assume dmode can then 'adjust' these values to change the 
virtual drive # its addressing.  As booted, using the stock descriptor that 
came in the latest images, an attempted dir /sh returns a no permissions 
error.

I think this means that the virtual drive in question has probably never been 
formatted, but I could be wrong.

Now, my drive, a 1GB scsi, is I think half (500megs basic) and half (500 megs 
os9), and is at least for the os9 half, formatted as 4 sector clusters.

I note that the 'dmode /sh' output contains many values that are different 
from what a 'dmode /dd' does, in addition to a rather largish offset of about 
7900 in /sh, and 0000 in /dd. Are the basic virtuals located inside of the 
os9 'partition'.  I was under the impression it was the other way around all 
this time.

Where can we find a doc page that describes how to properly calculate and set 
all these variables in the /sh descriptor?

FWIW I'm having lockups while formatting the disc about 75% of the time here, 
this with the newest 30206 images.  There are some other problems too related 
to my occasionally oddball hardware, but one thing at a time.

Thanks Robert.
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-- 
Cheers, Gene
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