For a while now, I've noticed that the MAME emulation of Moon Cresta (although very good) doesn't quite reflect the game itself - at least in the attract mode. I was curious to find out what was the actual problem so I've spent some time comparing both.
So, I've taken a video of both running at the same time to try and isolate the problem - which I think I've now done.
Note that the arcade version runs slightly faster - so this has been taken into account when starting the PCB and emulated versions. This is so that the actual shooting bit in the attract mode is at about the same point - as this is where the problems lie.
As the waves start, both ships move the same - so no issues here.
It is the *firing* that is the problem.
As the first wave starts (at around 46 seconds), the ships fire consistently: 1 bullet, 2 bullets, 1 bullet, 2 bullets, 1-2-1-2 etc. The problem is the second wave. MAME continuously fires without a pause as the first wave ends and the second waves begins 1-2-1-2 etc.
However, on the arcade version, it does the following: 1-2-1-2...1 (pause as second wave begins) 2-1-2-1 etc. You can see this at around 53 seconds.
This causes the sequence to fail and MAME ends a few seconds later than the arcade version.
Not sure what in the emulation would cause this. but if we are after perfection, then it should be noted as a bug.
I suspect the actual game play is perfect so I think this only affects the attract mode.
This bug may also possibly affect Moon Quasar (which was a sequel to this game). I'll check it out.
God, I miss those dark, musty arcades ....