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do any games use both PSG and FM soundchips at the same time? if not... then why? why not use both chips at once?

Only the Japanese BIOS uses both. I guess it is rare because

- composing 9-12 track music is hard
- the Mark III was not guaranteed to have the FM unit, so the music had to have a PSG-only fallback
- most games thus had a PSG/FM dual engine that used the same data for both to save space, time and money - and thus only 3-channel FM

so it IS possible to make songs that use both PSG and FM at the same time... just its rare within the realm of games?

Certainly, just the same as you could make a NES game with 20 cound chips on board and run them all at once - nobody did, but there's no technical reason why it wouldn't work. As mentioned, no game uses both chips, just that BIOS (which is really the only piece of SMS software guaranteed to run on hardware with both chips).

I'm positive I've seem at least 1 game that used FM music with PSG SFX

Quote

if not... then why?

Wasting precious cycles on updating all those channels was probably not considered to be worth it for most games. Maybe for something like a title screen or an end-game credits theme. But there was also the issue of how much ROM (and RAM) space that the music would be allowed to use. Memory was expensive back then.

Quote

Certainly, just the same as you could make a NES game with 20 cound chips on board and run them all at once

Well, not exactly since nothing like that ever existed, while the FM-fitted Mark3/SMS actually was produced and sold. That's more like NSF vs VGM, where you can compose music for fantasy configurations for which there are no hardware (yet).

djbass wrote

I'm positive I've seem at least 1 game that used FM music with PSG SFX

This is quite common on the MSX. I can't see why it wouldn't be possible on SMS.

From the circuit diagram of the MKIII FM expansion on Enri's page it looks like the PSG audio would be heavily attenuated when FM is enabled. The Japanese SMS does mix the two properly (I traced out the circuit from Maxim's board scan).

Author	Message
alex_mauer Joined: 04 Jan 2010 Posts: 2	psg AND fm at the same time? Posted: Mon Jan 04, 2010 11:28 pm
alex_mauer Joined: 04 Jan 2010 Posts: 2	do any games use both PSG and FM soundchips at the same time? if not... then why? why not use both chips at once?

Maxim Site Admin Joined: 19 Oct 1999 Posts: 13409 Location: London	Posted: Mon Jan 04, 2010 11:39 pm
	Only the Japanese BIOS uses both. I guess it is rare because - composing 9-12 track music is hard - the Mark III was not guaranteed to have the FM unit, so the music had to have a PSG-only fallback - most games thus had a PSG/FM dual engine that used the same data for both to save space, time and money - and thus only 3-channel FM

alex_mauer Joined: 04 Jan 2010 Posts: 2	Posted: Mon Jan 04, 2010 11:42 pm
alex_mauer Joined: 04 Jan 2010 Posts: 2	so it IS possible to make songs that use both PSG and FM at the same time... just its rare within the realm of games?

Maxim Site Admin Joined: 19 Oct 1999 Posts: 13409 Location: London	Posted: Tue Jan 05, 2010 12:52 am
	Certainly, just the same as you could make a NES game with 20 cound chips on board and run them all at once - nobody did, but there's no technical reason why it wouldn't work. As mentioned, no game uses both chips, just that BIOS (which is really the only piece of SMS software guaranteed to run on hardware with both chips).

djbass Joined: 25 Jul 2007 Posts: 577 Location: Melbourne, Australia	Posted: Tue Jan 05, 2010 6:51 am
	I'm positive I've seem at least 1 game that used FM music with PSG SFX

mic_ Joined: 27 May 2008 Posts: 161	Posted: Tue Jan 05, 2010 9:11 am
mic_ Joined: 27 May 2008 Posts: 161	Quote if not... then why? Wasting precious cycles on updating all those channels was probably not considered to be worth it for most games. Maybe for something like a title screen or an end-game credits theme. But there was also the issue of how much ROM (and RAM) space that the music would be allowed to use. Memory was expensive back then. Quote Certainly, just the same as you could make a NES game with 20 cound chips on board and run them all at once Well, not exactly since nothing like that ever existed, while the FM-fitted Mark3/SMS actually was produced and sold. That's more like NSF vs VGM, where you can compose music for fantasy configurations for which there are no hardware (yet).

SLotman Joined: 30 Jul 2008 Posts: 40 Location: Brazil	Posted: Tue Jan 05, 2010 10:00 pm
SLotman Joined: 30 Jul 2008 Posts: 40 Location: Brazil	djbass wrote I'm positive I've seem at least 1 game that used FM music with PSG SFX This is quite common on the MSX. I can't see why it wouldn't be possible on SMS.

viletim! Guest	Posted: Wed Jan 06, 2010 2:53 am
viletim! Guest	From the circuit diagram of the MKIII FM expansion on Enri's page it looks like the PSG audio would be heavily attenuated when FM is enabled. The Japanese SMS does mix the two properly (I traced out the circuit from Maxim's board scan).

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