> There was no bug ... pokey had been converted to a cpu device and now faces the same > obstacles all cpu devices have in MAME: synchronisation.
Yes, you cannot convert chips to device execute interface and expect them to work properly. The pattern is broken, you will always end up with bugs like this.
> The only solution currently known to me is using cycle-exact scheduling.
Which is a kludge. It doesn't fix the problem entirely either as reads are instant in mame/mess.
Another solution would be to not convert it to a pattern that requires cycle exact scheduling.