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SubjectRe: PCI init issues
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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