PowerPak NSF mapper FDS implementation

[rainwarrior]

I've been testing out FDS rip NSFs on the PowerPak, and I've found a whole lot of them have problems. Here's a few random examples:

* Akai Yousai (fails to start)
* Bio Miracle Bokutte Upa (crash on track 2)
* Falsion (fails to start)

I'm curious about the FDS implementation on this mapper. I've ruled out problems with RAM writes being mirrored by bankswitching, which was indeed a problem for four NSFs but I have fixed those.

My hunch is that writes to $6000-7FFF are working fine, but NSFs that rely on writes to $8000-DFFF might not be?

Also, is there source code for the NSF mapper available? I wouldn't mind being able to investigate the issue on my own.

(Edit: just to clarify this problem appears the same with loopy's latest NSF mapper as well as the one distributed by retrousb.)

[loopy]

I looked at the code, 6000-DFFF writes are enabled for FDS.

[rainwarrior]

My initial hunch probably wasn't it. I don't think the three nsfs i mentioned actually write 8000-dfff. So, I really have no idea why they crash the powerpak without more info on its implementation. So far I haven't seen anything in there I think is special.

I see that the NSF player is open source, but it seems like the mappers aren't? If I'm mistaken, let me know, because I'd love to have a look at what's going on in there, but otherwise that's fine, I won't bother you by begging for it.