I got Radica’s Tetris booting, it didn’t like the initial Stack Pointer value in the 6502 core, which according to Mametesters is incorrect for the A2600 too.
So far only player 1 works, because it seems to connect player 2 via a serial connection or something similar.
Unfortunately, it’s barely playable at all, the controls are oversensitive so you usually end up moving the piece 2 squares instead of one. I want to convince myself that this is an emulation issue, but watching people try to play the real thing makes me wonder if the issue isn’t with the weird controllers it uses but the actual game code, because they seemed to be quite frequently overshooting where they wanted to put the pieces too. It’s difficult to believe it’s meant to be as bad as it is in MAME, and I’m hoping it’s some side-effect of not having whatever player 2 needs hooked up, although I’m not actually optimistic.
I also added preliminary sound to the driver, although it doesn’t play the music in Tetris yet because I think it’s relying on the sound chip generating interrupts (or possible just a timer interrupt) which isn’t yet supported. Also my ADPCM decoding is wrong, I havn’t figured out the format (it’s not the usual OKI one) so it sounds awful at the moment anyway.
I also made a video of the Space Invaders one, with me playing Phoenix to demonstrate the current state of the sound emulation there. Be warned, cover your ears ;-)