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Re: PCI Bus Add on card
- To: Mailing List Recipients <pci-sig-request@znyx.com>
- Subject: Re: PCI Bus Add on card
- From: rwalter@Auspex.Com (Richard Walter)
- Date: Fri, 2 May 1997 12:19:38 -0700 (PDT)
- Resent-Date: Fri, 2 May 1997 12:19:38 -0700 (PDT)
- Resent-From: pci-sig-request@znyx.com
- Resent-Message-Id: <"tF1dE.0.ZY.XxZQp"@dart>
- Resent-Sender: pci-sig-request@znyx.com
>
> We are currently developing a PCI bus add on card, where we have two
> different PCI devices(chips) on it.
>
> Is it possible to support two different devices in just one PCI slot,
> without using a PCI-PCI bridge?
No.
> The problem is that there are only one IDSEL signal in the slot, and we
> need two IDSEL signals for the two chips.
There is also the issue of loading, trace lengths, arbitration req/gnt lines,
only a single clock line etc....
Oh, there is also the little minor issue that this is expressly forbidden by
the PCI spec. See section 4.4.3.4 on page 155 of the PCI 2.1 spec.
(Specifically the second bullet item: "It is specifically a violation of
this specification for expansion boards to: Attach two or more PCI devices
on an expansion board, unless they are placed *behind* a PCI-to-PCI bridge.")
> Thanks
Sorry.
> Claus Larsen
-Richard Walter
rwalter@auspex.com
Note: I speak for myself, not for Auspex.
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