[Coco] Boot flexibility in OS-9

[Robert Gault]

Several people have on their wish list a way to easily select a variety 
of OS-9 boot files or a way to change the content at will. Changing the 
content on boot at will has not been done to my knowledge but the 
functional equivalent is fairly easy to achieve.

One approach is to increase the effect size of OS-9 system memory and 
put every conceivably needed module in os9boot. I'm not sure but think 
that NitrOS-9 LevelIII may have increased system memory. If not, that is 
on Boisy's "things to do wish list" for NitrOS-9 in general.

A second approach, which can be done now for any OS-9 system, just 
stores as many boot files as will fit on a floppy and from Disk Basic 
permits selection of any of these boot files from a menu. RGBDOS or 
HDB-DOS makes this even easier because you can have up to 255 (or more) 
disks with just boot files which is a lot of choices.

I have written such a Disk Basic program for the Coco3 and someone else 
(can't remember who) has written similar software. The technique is 
simple and requires: 1) program to read an OS-9 root directory from Disk 
Basic; 2) present the directory on screen for arrow or joystick file 
selection; 3) determine the LSN/track# of the selected file; 4) present 
the information to LINK.BAS or a similar routine; and 5) change LSN0 
either on the disk in use or hard drive so that DD.BT (starting LSN of 
boot file) points to the selected file.

The files don't need to be named os9boot (obviously), the names should 
be descriptive of the content, but the files must not be fragmented. 
That means you use os9gen or the program of your choice to create a 
desired boot file, and copy it to a fresh disk with the name of your choice.