nelson@sun.soe.clarkson.edu (Russ Nelson) (03/03/90)
I'll bet that you already know that IRQ 2 on the AT bus is mapped to IRQ 9 on the slave 8259. You may even realize that the IRQ 9 handler simply issues an EOI to the slave controller and calls the interrupt associated with IRQ 2 (INT A). This ensures that software written for the PC will work when you use it with IRQ 2. But what I'll bet you *didn't* realize was that IRQ 9 is enabled at boot time. If you have a piece of hardware that generates a spurious IRQ 9 at initialization time, it will get handled by the default IRQ 2 handler. This interrupt handler may not do anything useful. In my case it crashed my machine. My solution is to disable interrupts during the time that I'm initializing the board. -- --russ (nelson@clutx [.bitnet | .clarkson.edu]) Russ.Nelson@$315.268.6667 Violence never solves problems, it just changes them into more subtle problems