Discovered why 33 Eyes - Seima Korin Den doesn't work.
Basically, 0x8128 is the IRQ vector, hence it fires the IRQ but it mustn't. If you comment out line 126, game boots and works fine ...
Stay tuned for a reason about why it fires that.

EDIT: Now it's official, MAME irq system sucks ass, because 3x3 Eyes does something VERY demented / twisted (take your pick). It has the NMITIMEN enabled all the time (0xa1), then it DISABLES the register (by writing 0x00) and executes a CLI opcode. Spurious IRQs happens due of that, because MAME, for whatever reason, remember that the irqs are called when in STI-mode.

Fun.

Last edited by Kale; 04/02/10 03:57 PM. Reason: More info about 3x3 Eyes