[Coco] A CoCoSDC alternative to the Drive Switch button

[Robert Gault]

  The CoCoSDC has a button on the circuit board that when pushed can swap mounted disks on drive #0. 
That is better than an actual disk swap on a Coco but is almost impossible with the wrong type of 
case for your CoCoSDC.

  Some OS-9 programs such as Interbank Incident by Tandy were designed to run from a hard drive as 
well as the floppies that come with the game. Using the COPYBANK command that comes with the game, 
you can set up, for example, the directories /DD/Games/IBI and /DD/Games/IBI/CMDS and transfer the 
contents of the three game disks to these directories on your hard drive.
  I have found it convenient to copy the .vhd I use with MESS and VCC to the CoCoSDC. I have worked 
out two methods for running IBI on the CoCoSDC without disk swaps or button pushes. The first has 
the .vhd mounted in drive0 and an IBI boot disk in drive1. The second has the boot disk in drive0 
and the .vhd in drive1. I suspect that anyone wanting to use the .vhd and HDBDOS on the CoCoSDC will 
have a .cfg file with the .vhd in drive0 so I'll describe that.

  So, the new boot disk takes somewhat more work with the .vhd in drive0 but here is how it can be 
done. First the game is a LevelI V2 OS-9 product and probably won't run under our current NitrOS-9 
LevelII systems. That means you need the software in the original OS9Boot file. Luckily the LevelI 
versions of rbsuper and llcocosdc work with OS-9 LevelI V2. Unfortunately Boot needed to be changed 
to work with drive1 instead of the default drive0.
  I extracted Boot from T34 on the disk, disassembled it, and change all input to $FF40 to drive1, 
and placed Boot back in T34. OS9Boot was separated into it's modules and I deleted D0, RS232, T1, 
PRINTER, and P (as my Coco just has 512K and I did not an Out of Memory error) and merged the rest 
with rbsuper, llcocosdc, and ddsd0_cocosdc (renamed to H0) into a new OS9Boot file.
  You can use dEd to change $44,$C4 (DD) to $48,$B0 (H0) in the ddsd0 file as the game docs imply 
that /H0 is hard coded in the game. I deleted the original OS9Boot, copied the new OS9Boot to the 
boot disk, and adjusted LSN0 for the new DD.BT and DD.BSZ values. I also deleted from the root 
directory the file "floppy" and made sure the one byte file "hard" was present.
  The startup file was edited to read:
-x
chd /h0/games/ibi; chx /h0/games/ibi/cmds
ex bank

  Now with my .vhd in drive0 and the new IBI boot disk in drive1, DOS1 starts the game and it never 
asks for a disk swap.

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I would have preferred to actually place the new Boot disk in the Basic section of the .vhd which 
would have made things simpler. I've not yet been able to get that to work.

Robert