Gonzo the creator of DColem has released a no sound demo of his port of an Atari 2600 Emulator for Dreamcast here is what he says:

I finally got my port of v2600 running.
Tested it with pitfall and donkey kong and the emulation runs quite well.
Still have to implement the controls and sound output.
I’ll release a little “no-sound” demo later today if everything works out well.
hell it’s real fun to play these classics again on my tv heh

The emulator at the moment can only be played through a coders cable,unless one of you great people out there can help us out,to download the emulator and add comments,thanks and suggestions ,go to this topic in the Classic Emulators Forum here