[Coco] Dragon SuperDos and Drivewire....

[Bill Pierce]

Phill, I'm sure Mr. Gault will chime in if I'm wrong... As he's the best source for HDBDOS info.
HDBDOS under DriveWire will allow 256 "disk" images in one of 256 VHD images.
The 256 disk images are accessable as normal "dirves" i.e. DRIVE0, DRIVE1 - DRIVE255.
The (theoretical) 256 (usually 4) VHD images can be accessed one at a tive via DRIVE#0, DRIVE#1 etc.
These commands can be issued from a basic program with no effect on memory, so some have written utilities to access, copy, move etc. files from one VHD to another. Though it has to be done at sector level to keep from destroying the program space, 256 bytes at a time.
Now, the cool feature is DRIVEON, DRIVEOFF. This (DRIVEOFF) allows you to access real floppy DRIVEs 0-3 and 4-255 disk images. Where DRIVEON turns real floppies off and uses 0-255 disk images on DRIVE#xxx.
Aaron Wolfe can explay how to manipulate Drivewire even further to access various offsets of various drives to get unique combinations. I have yet to have a need to play with this feature but expect I'm gett ready to.

Hope it helps
Bill P

Music from the Tandy/Radio Shack Color Computer 2 & 3
https://sites.google.com/site/dabarnstudio/
Bill Pierce
ooogalapasooo at aol.com




-----Original Message-----
From: Phill Harvey-Smith <afra at aurigae.demon.co.uk>
To: coco <coco at maltedmedia.com>
Sent: Thu, Oct 18, 2012 5:06 pm
Subject: [Coco] Dragon SuperDos and Drivewire....


Hi All,

Here's the problem, I'd like to try dropping the Drivewire routines into 
SuperDos, so that that DragonDos disks could be accessed via a Drivewire 
server.

However at the lowest level I/O SuperDos deals with cylinders, heads and 
sectors, whereas DW is completely LBA based. Now SD does record the 
geometry of a disk in it's directory track, however this is track 20, 
this is of course read when a disk is first accessed as on a physical 
disk it is always in the same place c=20,h=0,s=1.

With the standard emulator format files which used interleaved sides, 
this will mean for a double sided image that the directory track will be 
in a different position to the single sided image, which would be a problem.

Is there a call in the currently existing DW protocol to get this 
information from the image ? Or to get the file data length of the 
image, even the max LBA sector number would give a hint.

Or if anyone has any suggestions of a way of dealing with this problem ?

As far as HDB-DOS goes, I gather from various things that I have heard 
on here that you can have up to 255 virtual disks, are these all 
accessible at the same time, or do you need to mount up to 4 images that 
act as if they where 4 physical drives ?

Cheers.

Phill.

-- 
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !

"You can twist perceptions, but reality won't budge" -- Rush.

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