Well I haven't posted in awhile, and I just did a little work on the infamous Gimmick cart.
Turns out the sound hardware on it appears to really be a copy of an AY-3-981x down to the noise generator and enveloper.
I have to run more tests on it, but the enveloper works and the noise gen works, including the 5 bit prescaler for it, and the ability to turn it on/off in the mixer control register.
I have to see if the envelope gen is 4 or 5 bits though. A real AY chip is 4 bits and the Yamaha copy is 5.
Turns out the sound hardware on it appears to really be a copy of an AY-3-981x down to the noise generator and enveloper.
I have to run more tests on it, but the enveloper works and the noise gen works, including the 5 bit prescaler for it, and the ability to turn it on/off in the mixer control register.
I have to see if the envelope gen is 4 or 5 bits though. A real AY chip is 4 bits and the Yamaha copy is 5.