[Coco] VI and VIRQ
robert.gault at worldnet.att.net
Wed May 14 08:37:55 EDT 2008
Mark Marlette wrote:
> offset, virtual drive, etc.....Boisy is the expert on this feature...
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
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