[Coco] double-sided floppy setup in OS-9

[Robert Gault]

Chad H wrote:
> I'm wondering if someone can get me started or point me in the right
> direction on this.  I've been predominately a DECB user but have had OS-9
> for a long time, just never really gotten into it.  I would like start
> learning more about it but one thing bugging me is my floppy drive access.
> Currently I have 2 x 5.25 Double sided 5.25 floppies in my FD-502 enclosure.
> I'm using modified DECB EPROM to access them as 0,1 for top drive and 2,3
> for bottom drive.  When I load OS-9, it exhibits the same problem as DECB
> used to, can only seem to access one side of one drive.  I've heard there is
> some sort of device descriptor files or something that needs set but I have
> no idea how to go about doing it.
> 
>  

In essence, you need to modify the OS-9 floppy driver just as you 
modified the DEC ROM; ie. change the drive masks. You may want to have 
descriptors which will access a normal two sided disk and some for your 
special "double singles" disks. If that is true, then you will need to 
create additional descriptors.

The specifics of which bytes to change in the driver will depend on the 
version of OS-9 in use. You should post the OS-9 version and the Ident 
info on the driver. Then we can tell you how to modify your system or 
send you the modified driver and new descriptors.

Just be sure to indicate if you really want your disks to be "doubled 
singles" (the equivalent of 4 drives) or would be happy with the 
standard double sided 40 track disk (and have two drives).