Sound emulation in Panasonic FS-A1WX MSX2+ machine with turbo

By santiontanon

Master (250)

santiontanon's picture

11-04-2017, 00:58

Hi!

As reported by wyrdwad in this thread ( https://www.msx.org/forum/msx-talk/general-discussion/tales-... ), it seems that when the turbo is activated in Panasonic FS-A1WX MSX2+ machines, the frequency of the sounds made by the PSG seems to also be increased. I was trying to program a fix for that issue in Tales of Popolon, but in OpenMSX such frequency increase does not happen. I was just wondering if this is an unemulated feature, or if that might just be happening in some machines and not in others?

Thanks in advance! :)

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By Meits

Prophet (4080)

Meits's picture

11-04-2017, 02:31

This happens to all Panasonic MSX2+ machines. And since the frequency is not exactly multiplied by two, the pitch is out of tune if you play music that supports both FM/SCC and PSG. Microcabin and Konami games suffer this issue quite a lot.
But at least the tone is clean, just higher.
This can not be said of the turbo 7MHz kits (at least the ones around here in Holland) as they switch back to 3.5MHz a lot which makes the PSG go totally bananas.
For the Panasonic MSX2+ machines there might be a fix since you can read in which mode the machine is and multiply the pitch roughly by 5,37/3,57 (these figures probably have more decimals).
Actually this "feature" should've been emulated indeed.

By santiontanon

Master (250)

santiontanon's picture

11-04-2017, 02:59

hmm, if the frequency is multiplied by 1.5, that's going to be problematic, since dividing by 1.5 will be problematic (I was hoping it was just double, and I could solve it by just shifting the PSG values 1 bit to the right if Turbo was activated). But in any case, yeah, it'd be nice to have it emulated, to play around with a few ideas to see what works best Smile

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