[Coco] Dragon & Drivewire

[Phill Harvey-Smith]

Hi all,

Earlier this week I managed to boot my dual personality Dragon 64 (using 
the CoCo2 roms) over Drivewire, using a simple level converter circuit 
which takes the 3 lines used by the bitbanger and converts them to RS232 
voltage levels (Max202).

I was able to boot at the 56K baud rate, and everything seemed to work 
fine.

One thing I did wonder is why the CoCo1 is limited to 33K whereas the 
CoCo2 and the Dragon it seems can reach 56K ? Is this due to the CoCo2 
having better transmission circuitry than the CoCo1, which IIRC uses 
op-amps as level shifters. If this is the case then retro-fitting the 
max202 circuit to a CoCo1 might enable it to also reach 56K. I'll give 
this a go at some point.

Next up I guess is to take the DW bitbang routines out of HDB-DOS ans 
see if I can insert them into SuperDos, as this would allow the Dragon 
to natively use a DriveWire server. Though the complicating factor here 
is that DragonDos & SuperDos, unlike RS-DOS allow 4 different disk 
formats SS40, SS80, DS40 and DS80. The problem being of course that SS80 
and DS40 are the same size :( NitrOS9 handles this because it just uses 
LBA rather the CHS.

In other news, I now have DragonMMC working on the CoCo, this is able to 
load cas files by patching the ROM to load from the MMC card, so a 
typical cas game loads in a couple of seconds. Since it also has 32K of 
ROM, it can soft load cartridges, this is how I booted over DW, 
sofloaded the HDB rom and then typed DOS.

Cheers.

Phill.