[Coco] Introduction

[Jayeson Lee-Steere]

Thanks for the welcome all.

My project is an emulator targetted at  Dungeons of Daggorath. I've wanted
to write an emulator for a while and the recent Global Game Jam theme of
"heartbeat" inspired me to take a crack at a reduced emulator for
Daggorath. Apart from wanting exact gameplay, I have a few other things I
want to try that don't affect the game. I have a CPU core done and have
been digging through data sheets to figure out the VSYNC timing. I have
also created a partial replacement for the basic ROM so I can distribute
the package unencumbered by copyrighted ROMS. I think I have written more
6809 on this than I ever did back in the day, but modern tools and a vast
array of searchable references make things go quickly. It has been a blast
so far.

Daggorath is extremely timing sensitive and no emulator I've tried gets the
attract sequence exactly right. I think. XRoar is very close to Coco 3
videos available but I'm not sure which one is off. The sequence on XRoar
is actually better than what shows on the Coco 3 - you can hear the
wizard's image close by and it ends with a knight and stone giant in front.
I suspect I will probably need to trace a real Coco with a logic analyzer
to get things right. And that is where a North American Coco becomes
important. The 50Hz PAL refresh is completely wrong and you get an attract
sequence with almost empty hallways and gameplay will be very different
also. (It occurs to me now that most games I've played probably do not play
as their developers created them). Plus, I have never seen NTSC artifact
colors in person and they are certainly not like PAL artifact colors
("press result until the screen is red" was not idea for our market).

I do actually have some ideas for a modern Daggorath inspired first person
game. Maybe one day.

Regards,

Jayeson