Playing three songs from Ys II for the X1 Turbo on the MSX. Recorded straight from the Yamaha SFG-01 FM Sound Synthesizer Unit (YM2151 OPM) and the internal AY-3-8910 PSG.
Also, you may notice that it is playing VGZ files :).
By the way, prior to recording I slightly modded my Yamaha SFG-01 to not output mono sound to the MSX, so I could properly mix the mono PSG and stereo OPM sound. There was an airwire between the stereo and MSX outputs so I didn’t need to cut any traces, just desoldered the wire. While opening it up, I noticed a previous owner seems to have been in there before and added a little upgrade daughterboard with the SFG-05 ROM… Nice!
The music of Ys II for X1 Turbo is quite identical to the PC-88 version by the way.
The PC-88 uses an YM2203 OPN which is essentially a cut-down OPM (mono, and three 4-op FM channels in stead of 8) with an integrated PSG. So it doesn’t use the OPM to its full potential as 5 of the eight OPM channels are not used :). On the plus side, you do get nice stereo!
In the future I would like to try to emulate the OPN on the OPM and PSG, they’re quire comparable and the OPM only lacks 1 feature which is hopefully not used too much.
PSG and SSG are just two names for the same thing.
PSG is often used also to name the Texas instruments sound generator chip (Digital Complex Sound Generator or DCSG for short) SN76489.
The original way General Instruments called it's AY-3-8910 was "PSG". Yamaha used to call it's variant "SSG", I believe that was because "PSG" was actually trademarked at the time.
This wikipedia page explains a bit of the confusion:
The Yamaha YM2149 SSG is a Yamaha clone of the General Instrument AY-3-8910 PSG. Some MSX machines use the PSG others use the SSG (often built-in to the MSX-Engine). The only real difference is that the envelope generator of the SSG has twice the resolution of the PSG, but in terms of control they are identical. The VGM files contain information which variation of the PSG is used, so this is what I display, but otherwise I do not treat them differently.
Apparently, only if the music uses a lot of envelopes, you will notice because envelopes behave differently (higher resolution on volume transitions for envelope generator, there's twice as many on the YM2149 as the AY-3-8910) on the Yamaha chip.
That might not even matter much on slower computers like the MSX but on computers like the Atari ST (which uses a faster 68000 CPU and has timers) higher resolution envelopes would be a big thing.
Btw, the Turbo-R has a Toshiba chip engine and that has a AY-3-8910 equivalent inside, not a YM2149 equivalent. So even though the Turbo-R has timers and a fast CPU, it has the old AY in it instead of the YM.
On machines with V9938 VDPs I implemented a 300 Hz timer using line interrupts. This means the VGM playback is timed more accurately on MSX2, MSX2+, and a few MSX1 machines.
With this, I also removed the automatic switch to 60Hz and the /5 option to manually select 50 Hz, because there’s no longer a need for it.
