Re: Fixing IO Base and IRQ

["Monish Shah" <monish.shah@indranetworks.com>]

> I need some advice.
>
> At present, the application depends on a fixed Base IO address and IRQ.
The
> card is an ISA card and the OS is DOS.  Since the ISA bus has disappeared
> from current PCs, a PCI equivalent card needs to be designed.  To minimize
> the impact on the software it is desired that the Base IO address and IRQ
be
> the same as that on the ISA card.  From Tom Shanley's book, the Base IO
> address can be fixed by using a legacy class code and omitting the Base
> Address Registers on the card.

Is there anything in the PCI spec to support this?  I don't remember seeing
it.  Unless you can find a basis in the spec for doing this, you should not
do it.  (Unless, your application is for internal use or something like that
where it can't screw over innocent users, in which case you can do what you
like.)

> What I can't figure out is how to fix the
> IRQ.  I believe that the BIOS selects the IRQs to associate with PCI
> interrupts and the application has no control over that.

You are right.  You can't fix the IRQ.

> Does anybody out there have any idea how to fix the IRQ and Base IO
address
> on a PCI system?

How about changing your software to find out the IRQ and the Base IO
address?  Then you don't have to fix anything, which is the right way to do
it.

Monish Shah
CTO, Indra Networks

> Thanks,
>
> Scott Davis
>
> _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/
>
> Scott Davis
> Principal Engineer
> TechniQuest Associates
> P.O. Box 1822
> Nevada City, CA 95959
> (530) 263-1314
> (530) 265-9589 (FAX)
> scottd@techniquestassociates.com
> www.techniquestassociates.com
>