Slight differences in YM2612 emulation

[ICEknigh7]

(Crossposting from Mametesters)

I've recorded what may be a good test case for the YM2612's "ladder effect", a track from Earthworm Jim 2 which Tommy Tallarico has mentioned was made specifically to exploit said effect (I'm assuming to add to the cringiness of the level where it's used): https://youtu.be/V2he1ez_JKc

Hardware used: Japanese Mega Drive VA1 (note that this may accentuate these effects, in comparison with later hardware revisions) Sound in the video was amplified by 20dB, since Mega Drive recordings tend to sound pretty faint.

Steps to reproduce in MAME: Load the genesis driver with the game "ejim2u" and then open this savestate (created in MAME 0.240) or:

• Start a game
• Pause, then enter A, C, C, A, B, A, B, Left to enter the sound test
• Select the sount test, press A until the track number is 0
• Press C to play the track

[franciscod]

Some other examples here (thanks genatari!)

https://www.deflemask.com/bugs/view.php?id=121

[EdyGH36]

https://user-images.githubusercontent.com/50022298/156891136-e1bc2854-c6a1-4e7d-8154-8a8d63f59320.mp4

Ladder Effect differences above. The ymfm core cuts the PWM sweep on very low levels.

[aaronsgiles]

Thanks for the comparison, @EdyGH36. That is very helpful. Do you have a VGM or other description of the registers programmed so I can generate the same WAVs myself?

[EdyGH36]

LadderEffectDiagnosticsTone.zip