Hey there, I posted a question in the Engineering Q & A thread, but I think it was misplaced and not related, so I decided to post a topic here. I'm looking for any good documentation for the Dreamcast VMU. I've already found an assembler, disassembler, and a VMU emulator w/source code. I found a handful of documents already, but they're pretty incomplete. I'd like to see if anyone has anything else that could be of use. If anyone wants, I'll link to the docs I already found. Any help is really appreciated!
Don't have any doco, but apparently Watermelon have got 3 shades of greyscale working using "special tricks" and have overclocked a VMU to 600kHz
Grayscale isn't really a special trick, they're just taking advantage of the slow refresh rate on the LCD. They're rapidly turning the specific pixels on and off faster than the pixels can update, so the in-between state kind of blurs together like it's grey. If they did the same thing in an emulator you'd just see those pixels flickering. This trick is used in a lot of games for graphing calculators, for the same effect. And from the documentation I've looked at, I don't think the 6mhz mode is actually considered overclocking it. The VMU has a couple of timer interrupts, which make the rapid updates pretty easy to do. You might find some additional useful information in the archives of the Vmu-dev mailing list. One of Sega's developers regularly posted to the list when it was active: http://gamesource.groups.yahoo.com/group/vmu-dev/ The official SDK tools were unofficially released and the guy from Sega had no problem with them being passed around at the time. That being said, Marcus Comstedt's unofficial documentation and tools are pretty much the only thing you need to develop for it: http://mc.pp.se/dc/vms/cpu.html Sega's official tools and emulator can be found in the Dreamcast SDK.
