[Coco] VCC and HDBDOS

[Robert Gault]

Kip Koon wrote:
> Hi Robert,
> I perused your web site a few days ago and found that I was confused as to which version of RGBDOS I need for VCC 2.00.  Of all the RGBDOS rom files I saw, I could not find one for VCC.  Maybe I missed something in my search.  Thanks for any help you can give.
>
> Kip Koon
> computerdoc at sc.rr.com
> http://www.cocopedia.com/wiki/index.php/Kip_Koon
>
Kip,

  There are very few differences amongst the "versions" of RGBDOS. The primary 
one is that some emulators require a ROM header indicating where the ROM should 
load into memory. All of the JVC emulators require a two byte prefix in Intel 
format equal to the load address. For example, a disk.rom must start with $00C0.
  All the other emulators Keil, MESS, VCC expect an exact copy of the ROMS 
without any prefix.

  There are some other differences in how closely an emulator matches a floppy 
drive. On a real Coco, if you change the drive table from $1,$2,$4,$40 to 
$1,$2,$41,$42 you change from four single sided drives to two double sided drives.
  When Joseph incorporated RGBDOS into VCC, he used a RGBDOS version that was 
set for double sided drives and had to change back to the original single sided 
table.

  There is a difference between VCC and the JVC, MESS emulators in that VCC 
mounts a single .vhd hard drive while JVC and MESS can mount two. There are 
different versions of RGBDOS for handle that.

  One final problem occurs if you want to use VCC with Drivewire. For that, VCC 
must be set to use hdbdw3bc3.rom rather than rgbdos.rom.

  Some of these issues occur when using RGBDOS/HDBDOS on real Coco hardware and 
get more complex when adding a CocoSDC or similar hardware.

  As far as VCC 2.xx goes, you want a version for a single .vhd hard drive with 
an offset of $5A000 at $D938. It won't hurt to have the two .vhd drive version 
as you are not likely to use the command to switch .vhd drives.
  The ROM image should NOT have the two byte header. It should start with the 
typical DK.

==========
If you can't get a version to work or you have problems, contact me directly and 
I'll try to send you something that does work.
If you just enjoy tinkering :) you can extract RGBDOS from the older versions of 
fd502.dll where the ROM starts at byte $12030 through $14030.

Robert