[Coco] Possible VCC add-ons/additions

[Robert Gault]

Paul Fitch wrote:
><snip>
> On the COCO/OS9 hardware side (not VCC's problem at all) it would be nice to
> access floppy disk images on the HD as if they were real Floppys.  Tho this
> is probably not needed as HDB sort of alreay does this.  Or can OS9 not talk
> to the HDB disk images on the HD?
> 

This is a trivial issue which anyone that programs for OS-9 can do on 
their own. Cloud-9 already has software that communicates with OS-9 
drives in the Disk Basic partition of a .vhd image. I have also written 
software that does the seem thing on my real RGBDOS hard drive system 
and under emulation.

  All you need to do is add a constant offset to all LSNs when doing 
this type of I/O. You can use emudsk.dr as your source code template. 
Just add a routine to alter the LSN values. You can either use a fixed 
offset or make it a variable taken from the descriptor for the Disk 
Basic partition on an HDBDOS/RGBDOS hard drive system. By default, all 
.vhd drives have 368,640 OS-9 sectors and at least one 256 drive Disk 
Basic section of 161280 sectors. The same is true for real HDBDOS/RGBDOS 
hard drives. With a large enough drive, more space can be used for 
either OS-9 or Disk Basic.
  I've even written a modification of PCDOS (OS-9 program that reads IBM 
type floppies) to read Basic formatted disks from the Disk Basic hard 
drive partition.