> huh? PULSE_LINE is not unusual, it's for edge triggered interrupts. IMO the > almost-always-wrong type in MAME is HOLD_LINE.
Even for CPUs with edge-triggered interrupts, circuits that pulse the IRQ line are pretty rare (it's extra gates). Usually the line is only triggered by an edge in one direction so the peripheral goes low->high and that trips the CPU. Then you ack it and the line goes high->low so other sources may drive the line.