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Date:      Fri, 17 Jan 1997 00:26:39 -0700
From:      Steve Passe <smp@csn.net>
To:        Kenneth Merry <ken@housing1.stucen.gatech.edu>
Cc:        smp@freebsd.org
Subject:   Re: Adaptec 3940UW and SMP 
Message-ID:  <199701170726.AAA15776@clem.systemsix.com>
In-Reply-To: Your message of "Fri, 17 Jan 1997 01:36:34 EST." <199701170636.BAA22619@housing1.stucen.gatech.edu> 

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Hi,

> 	Well, the manual isn't very revealing about whether there are
> actually one or two PCI busses on the board.  The 5th slot is a a "shared"
> PCI/ISA slot, and it also has an ASUS MediaBus connector in line with the
> PCI connector.  Here's what the board manual says about slot 5 and
> interrupts:
> 
> "IMPORTANT: PCI Slots 4 & 5 share the same IRQ.  If using PCI cards on both
> slots 4 & 5, make sure taht the drivers support "Share IRQ" or that one
> card does not need an IRQ assignment.  Conflicts will arise on PCI Slots 4
> & 5 taht will make the system unstable."

so it appears that you might be able to put the 3940 into slot4 and the
vga into slot5, the SMC in any of the others, and have 2 free, usable slots

---
> 
> 	In the bios, you can hardwire the interrupt for slots 1, 2, 3 by
> themselves.  Slots 4 and 5 are lumped together, one IRQ for both.  This
>  ...
> 	That comment is in the section that talks about the bios interrupt
> assignment stuff.  So, based on what you said, and the fact that it doesn't
> assign another IRQ to that slot, I'd bet that they just tacked on another
> slot, and didn't put a bridge chip on the board.  (just a guess, I could be
> wrong of course. :) )

so this is where I get a little confused... I thought in the past the
typical board limitation of 4 PCI slots was based on the LINE[ABCD]
situation.  Early PCI MBs sometimes used LINEA for slot1, LINEB for
slot2, etc.  I was thinking that now they route the LINEA pin from each
card to the LINE[ABCD] inputs of the PCI_ISA bridge chip, hence the magic
of the number 4.  Is this so, or do these PCI slot/LINEA INTs go directly
to the MB ISA redirector hardware?  If so, what is magic about 4 (slots)?
Stated another way, why does the 5th slot need to be shared?

--
Steve Passe	| powered by
smp@csn.net	|            FreeBSD




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