Michael Richardson <mcr@sandelman.ottawa.on.ca> writes:

> 
>   Are you sure that edge triggered interrupts can be shared between
> multiple *ISA* cards?

Yes, but it depends on the card.  For example, many add-on serial
cards and SCSI cards use open-drain outputs which specifically support
sharing of IRQs.

The result is that in some systems, there is specific support for IRQ
sharing on particular devices.  If the software doesn't happen to know
that a device supports IRQ sharing, then it can't do it.  And
typically you can't share IRQs between two different cards of the same
type (e.g. two SCSI cards from different manufacturers).  That's
always seemed extremely bogus to me, so I didn't do it that way.

If you configure the machine wrong, you can fry it with or without
running NetBSD, so I don't consider this our problem.  The software is
specifically designed to err on the side of allowing you to do stupid
things.

>   The 509 is software programmed, the AST is, as you surmise, set by
> jumpers. 

The 509 gets its settings from NVRAM.  I would consider it highly
bogus for our software (or any other) to simply reconfigure the card
as it sees fit.  If you want plug-and-play, then use plug-and-play.
(Yes, I realize we didn't have a PnP driver in 1.2, but that doesn't
change the point.)