Subject: Re: problems with autoconfiguring 3c509 cards on -current
To: None <current-users@NetBSD.ORG, port-i386@NetBSD.ORG>
From: Mike Wozniak <>
List: current-users
Date: 01/28/1997 09:29:47
On Mon, 27 Jan 1997, Jason Thorpe wrote:

> NetBSD has IRQ staring; i.e. interrupts of the same type (LEVEL
> or EDGE) can be shared.  (PULSE can't be shared with anything.)
> Both the ast and ep use EDGE triggered interrupts, thus the line
> can be shared.

That's a dangerous little piece of advice considering the only way 
interrupts SHOULD be shared are if the bus and adapters are specifically 
designed for it with open collector outputs on the IRQ lines.  PCI and 
Microchannel were, ISA was not.

There are some hardware hacks out there that allow you to do this and 
many other times you just get lucky that you didn't fry one or both of your 
cards.  You should be pretty familiar with the circuitry before you 
attempt this.  

The software support of shared IRQs is inconsequential...

Michael S. Wozniak, Systems Developer, Secure Computing Corporation
e-mail:, web: