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Date: Tue, 4 Mar 2003 18:36:26 -0500 (EST)
From: Donald Becker <becker@scyld.com>
To: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
cc: jamal <hadi@cyberus.ca>, Greg KH <greg@kroah.com>,
       Linus Torvalds <torvalds@transmeta.com>,
       Jeff Garzik <jgarzik@pobox.com>, <kuznet@ms2.inr.ac.ru>,
       <david.knierim@tekelec.com>, Robert Olsson <Robert.Olsson@data.slu.se>,
       <linux-kernel@vger.kernel.org>, <alexander@netintact.se>
Subject: Re: PCI init issues
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On Wed, 5 Mar 2003, Ivan Kokshaysky wrote:

> On Tue, Mar 04, 2003 at 01:16:22PM -0500, Donald Becker wrote:
> > Incorrect.
> > Most quad Tulip boards have the bus bridge wired so that all interrupts
> > are sent on the INTA output of the board.
> 
> This can be true for older cards, but post-1998 hardware must follow
> the spec.
> PCI-to-PCI Bridge Architecture Specification, Rev 1.1, Dec 18, 1998,

The reality is that most quad Tulip boards were designed before 1999,
and therefore act as I described.

Most of the experience is with quad Ethernet adapters, as there are few
other common PCI boards with bus bridges.

> I know for a fact that at least D-Link card mentioned in some reports
> utilizes all four INT# lines, because I have one.

The D-Link board is 

>   Device 0 on a secondary bus will have its INTA# line connected to
>   the INTA# line of the connector. Device 1 will have its INTA# line
>   connected to INTB# of the connector. This sequence continues and
>   then wraps around once INTD# has been assigned."

This seems to be what most x86 BIOSes assume (almost all BIOSes use the
Intel reference code for PCI setup), even from 1995-era machines.
But again, this does not match how _most_ of the quad boards are wired.
Curiously, non-x86 machines usually work fine without the work-around,
meaning that they have a different interpretation.

-- 
Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Scyld Beowulf cluster system
Annapolis MD 21403			410-990-9993

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