Changes

Also, note that period = 0 is the same as period = 1. This is mentioned in the YM2203 datasheet. However, this does NOT apply to the Envelope period. In that case, period = 0 is half as period = 1. [https://github.com/mamedev/mame/blob/master/src/devices/sound/ay8910.cpp Source] (Does this last sentence apply only to the SSG or to the PSG as well?)

Things that have been verified not to halt things: [https://forums.nesdev.org/viewtopic.php?p=236745#p236745 Source]