The Z80 seems to process a "little bit" faster than it should, it's subtle though. The 68k is either overclocked beyond belief, or the bus access between the 68k and z80 is completely borked (I think the former). I'm also under the impression that the YM's DAC emulation requires the sample data to be sent to the chip at a specifically correct rate, 22,050hz seems fine, other rates seem to cause a bit of jitter, in fact, in the original Sonic 1 title, the drums sound off, almost as if they're playing at the wrong starting point (we know it's not a banking issue, as the samples in Sonic 1 are stored in the z80 itself, so it's something else). The PSG also sounds higher in tone by a touch, but that's probably just me... The emulation is not as bad as I thought it would be though, I was expecting raster H-blank effects (like slit scanning) to go to complete hell, but it seems to hold up somewhat OK. I'd imagine excessive use of it may cause unwarrented behaviour though. All in all, I am surprised.