[Coco] DW3DOS ROM not loading NitrOS9 correctly

[Robert Gault]

Chad H wrote:
> p.s.  Yes the NitrOSO .vhd on the server drive 0 is good.  Its what i have been going into all along by DOS command or a special floppy disk I made for my modified drivewire rom in my 502 controller.  That ROM has 'DRIVE OFF' by default at bootup so I can AUTOEXEC real floppies.  I have a floppy I made bootable in NitrOS9/DW.  Using this disk with the DOS command, it boots from the floppy for the first part of the boot process (till the screen goes blank with 'NITROS9 BOOT' in the center) at which time it finishes the boot from reading the DriveWire server's Disk 0.   So that image works in various situations... just not from the DW3DOS ROM I pulled from the Cloud 9 ZIP.
>
> Sent from my Transformer Infinity
>
> Chad H <chadbh74 at hotmail.com> wrote:
>
> The one I tried was "dw3dos_dsk_cc2.rom" from the archive on the Cloud 9
> site.  When booting that in EPROM, it does access the DriveWire server and
> reads a bunch of sectors and displays "NITROS9 BOOT" on the screen.  If I
> take the server offline before booting the ROM, it very quickly goes to
> "BOOT FAILED" on the screen.
>

OK, I just compiled DWDOS and have looked at the results but not yet tested the 
code on a real Coco, of any model.

You chose the correct ROM image to burn into an EPROM but the first thing you 
should have done is tried the LOADM version dw3doscc2.bin. This version will 
load code into memory at $2400 and execute from that address.

So, you need to tell us exactly what happens when you use the LOADM version, or 
if you don't have a disk system, what happens if you use the tape version 
(CLOADM) dw3doscc2.wav .
If either (C)LOADM version fails, then there is a problem with the code or the 
server settings. If either of these works, there is a problem with the manner in 
which you created your EPROM.

You have asked frequently about converting .bin to .rom images. I presume the 
real question is how to generate an EPROM.
The dw3dos_dsk_cc2.rom is a pure ROM image and can't be used with LOADM. It must 
be transferred to your EPROM programmer as is, to be burnt from $0000 to $1DFF 
on your EPROM.
I use the Disto MPROM Adapter with a Disto SCII disk controller. This device has 
no provision for acquiring data directly and the image must be a LOADM .bin 
file. In this case, the LOADM header/instructions place the file at $3000-$4FFF 
to be copied by the MPROM unit to the EPROM. So if I wanted to save a disk ROM 
for use with the Disto unit, the commands might be:
SAVEM"DISKROM",&HC000,&HDFFF,&HA027
LOADM"DISKROM",&H7000
The above commands would offset load the ROM image to $3000 ($C000+$7000=$13000) 
for the Disto.

Regarding the dw3dos_dsk_cc2.rom image, there is some code in it I've not seen 
in a Coco ROM.
sta $FFDA
sta $FFDD
This code will tell the SAM how much memory is present in the Coco. However, I'm 
under the impression that this info was hardwired with jumpers and these two 
bytes were not used. I've no idea what will happen if you POKE these bytes.

Robert