PicoDrive ssf mapper is broken? Problem with "SEGA SSF" in header

[corthax]

Rom that uses krikzz SSF mapper works fine, but only if there is no "SEGA SSF" in rom header but anything else.
The problem is that "SEGA SSF" is needed by BlastEm and Mega Everdrive to enable mapper.

[irixxxx]

I'm a bit puzzled. Can you explain in greater detail what needs to be done here?

[corthax]

There is the rom and SGDK source (rom.bin) https://github.com/corthax/mdtracker/tree/main/out
I'm using krikzz SSF mapper to enable 512Kb SRAM support on everdrive.
It works more or less ok in PicoDrive, aside from PSG noise is out of tune, also DAC panning doesn't work :), but only if "SEGA SSF" in header replaced with something else.
Otherwise seems I can't access SRAM properly for some reason.

[irixxxx]

Re PSG noise out of tune: there's a suspicious comment in pico/sound/sn76496.c at line 40. Are you able to make your own picodrive build? If so, changing the FB_PNOISE to 0x10000 might cure your problem.

[irixxxx]

Ah, there was a bug in the ssf2 mapper which prevents enabling the sram :-D. Could you possibly try the fix in libretro/picodrive:4867a33c8 and see if that fixes your ssf problem?

[irixxxx]

BTW, DAC panning and CSM are not implemented at all. Not sure if (and when) this is going to happen. It's surely not very high on my list ;-)

[corthax]

Hmm seems that SRAM problem is now gone :)

[irixxxx]

sounds good (hopefully ;-))