> Seems unlikely to me, video works fine with or without the card inserted.

Yeah, but we're not talking about video functionality, but the vbl
interrupt.  The vbl interrupt comes in as a nubus interrupt.  Those
are normally disabled until we find a nubus card that registers an
interrupt with the system (through the driver).  Configured ethernet
cards will do this.  Once the nubus interrupts are enabled, when they
are triggered, they must be handled and cleared.  If there are any
devices that do not clear interrupts, the system hangs (which is why
they're disabled by default).  The reason for this is that all "nubus"
interrupts are wired in a "wired-OR" configuration to one interrupt
signal on via2 (or via2 emulator in most cases ;-).  If any "nubus"
interrupt is active, the via2 interrupt is active.

I'll try to do something intelligent with Michael's information and
see if we can clear the internal video's vbl interrupt properly.  I'll
put up a test kernel for you folks.

-allen

-- 
              Allen Briggs - end killing - briggs@macbsd.com