Are you sure that edge triggered interrupts can be shared between
multiple *ISA* cards? I do not think that this is the case, which was
the classic faux-pas for PC ISA buses.
  Or is this really a 8259 programming issue? I'd understood that the
ISA did not spec open collector output (wired-or) for the IRQ
lines. Please let me know if my understanding here is wrong. If we can
in fact share interrupts across an ISA bus, then this is truly wonderful.
  The 509 is software programmed, the AST is, as you surmise, set by
jumpers. 

]                Physical location: Somewhere on planet earth!               [
]          Michael Richardson, Sandelman Software Works, Ottawa, ON          [
]        mcr@sandelman.ottawa.on.ca http://www.sandelman.ottawa.on.ca/       [
] panic("Just another NetBSD/notebook using, kernel hacking, security guy"); [