[Coco] CoCo Disk Drives

[Robert Gault]

Brian Blake wrote:
> Robert will correct me if I'm wrong, but, when issue the drive off command,
> it disables the DW access to floppies 0-4. Floppies 5 to 255 should still
> be available to DriveWire.
>

Exactly as already was stated. :)

If you want both floppies and Drivewire mounts, you should generally not mount 
any disks in the Drivewire 0 and 1 positions as you want drives 0 and 1 to be 
floppies.

Now things get more complicated if your hardware floppy drives are double sided 
and you want to use double sided disks. You also need to know what the default 
drive mask table values are for HDBDOS. You can find them in the HDBDOS source 
code and they are 1,2,$41,$42.
These values mean the the front sides of each hardware floppy are drive0 and 
drive1 while the respective back sides are drive2 and drive3. So for complete 
access to the floppies, enter DRIVE OFF and drives 0-3 will be floppies and 
drives 4-255 will be on Drivewire.

Now you don't have to enter the DRIVE ON/OFF commands if you use some tricks to 
automate things. You could also use a menu program where you can select what you 
want with a key stroke.
Remember I said the HDBDOS by default start with drives 0-255 on Drivewire or a 
hard drive. It will also automatically look for a Basic program AUTOEXEC.BAS on 
drive0 and, if found, will run it.
The program can be a menu or just a simple command. In your case you might want 
a one liner: 10 DRIVE OFF . Then any time you start your system with both your 
PC, Drivewire, and then the Coco running, you will automatically get the DRIVE 
OFF command and will have your floppies active. If you will only be using single 
sided floppies make the command: 10 DRIVE OFF 1 . Then you will have the front 
side of both floppies and Drivewire for 3-255.

Now that's not all you can do. If you don't want to use Basic, you can 
automatically boot NitrOS-9. In that case, you would mount a NitrOS-9 bootable 
disk on DW 4, either a .dsk or .vhd. The .dsk in DW0 would be a Basic disk with 
AUTOEXEC.BAS having  10 DOS4 . That would try to boot NitrOS-9 from DW4.
If you want to mount a .vhd type used with VCC or MESS that has the boot disk on 
a Basic drive say 254, that needs a slightly different approach.
The simplest method would require an HDBDOS ROM with an offset of $5A000 and the 
.vhd mounted in DW0. The AUTOEXEC.BAS on the .vhd could be 10 DOSn  where n is 
the drive on the .vhd where the boot disk is located.
Keep in mind that you must have a BOOT and /DD set for a Drivewire system.

A third alternate to permit using the standard MESS or VCC .vhd drive without 
requiring any changes to the .vhd would be to create a floppy boot disk for 
Drivewire and mount it in DW1. The floppy in DW0 would have  10 DOS1 , the BOOT 
on DW1 would be set for drive1, and the /DD descriptor would be equivalent to /X1.

Now if you want only Disk Basic and not NitrOS-9, you can still use a MESS VCC 
.vhd but need to place an offset value in the DW drive number of $5A000.

Robert



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