Hi There,

On anything with a 16 bit ISA bus (386 and above), IRQ 2 is the cascade
interrupt, to allow IRQ9-IRQ15 to exist.  Basically, AFAIK, anytime
IRQ9-15 is triggered, the second PIC triggers IRQ2.  For compatability,
the 16 bit ISA slot puts IRQ 9 on the same pin that IRQ 2 used to be on
the 8 bit slot.  As far as the card is concerned, irq 9 and irq 2 are the
same thing - only one pin.  You can't use IRQ 2 on a 386 and above, so on
the software end of it, you should never touch IRQ 2.  Some programs
assume that when you specify IRQ 2, you really mean 9. 

So, if you have a card configured for IRQ 2, tell netbsd it's using IRQ 9.

Rick

 On Mon, 21 Apr 1997, John A. Maier - MIS dept. wrote:

> Yes the old is it IRQ 2 or is it IRQ 9 dilemma.  If you go back to the original 8 bit ISA bus IBM PC and XT, on the PIC (Programmable Interrupt Controller) IRQ was unused.  Upon the advent of the IBM AT, the ISA bus became 16 bit and there was a need for additional IRQs.  So IRQ2 was used to chain a second PIC at IRQ 9 for additional IRQs.
> 
> So, at least in older equipment, IRQ2 and 9 are the same.  I can't comment on newer motherboard, because I haven't investigated the issue.
> 
> jam
> 
> ----------
> From:  Patrick Welche[SMTP:prlw1@cam.ac.uk]
> Sent:  Monday, April 21, 1997 7:27 AM
> To:  Leone Marco
> Cc:  netbsd-help@netbsd.org
> Subject:  Re: Two network cards
> 
> Leone Marco wrote:
> 
> > a local net in two subnet.
> > 
> > I've solved the irq and i/o address conflict, but the kernel doesn't
> > seem to recognize the card.
> > 
> > What shall I do to let the kernel see the second card?
> 
> Have you got both ethernet cards configured in your kernel config file
> in the same way you have set the jumpers on your card? Extract from mine:
> 
> ed0     at isa? port 0x300 iomem 0xd0000 irq 10 # WD/SMC, 3C503, and NE[12]000
> ed1     at isa? port 0x340 iomem 0xd8000 irq  2 #   ethernet cards
> 
> When I first tried this I had a mysterious unknown irq conflict with
> 11, still don't know from what. irq 2 in the above is detected as irq 9.
> 
> Hope this helps,
> 
>  Patrick
> 
> 

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Rick Byers                                      Internet Access Worldwide
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