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RE: PCI Load Question
- To: Mailing List Recipients <pci-sig-request@znyx.com>
- Subject: RE: PCI Load Question
- From: Andrew Ingraham <Andrew.Ingraham@digital.com>
- Date: Fri, 8 May 1998 10:12:56 -0400
- Cc: "'pci-sig'" <pci-sig@znyx.com>
- Resent-Date: Fri, 8 May 1998 23:12:22 -0700
- Resent-From: pci-sig-request@znyx.com
- Resent-Message-ID: <"l2gm22.0.2p7.xAnKr"@electra.znyx.com>
- Resent-Sender: pci-sig-request@znyx.com
There is no 10 load maximum in PCI.
You are probably thinking about the 10 effective load *recommendation*.
But the PCI Spec also mentions 16 loads as a possibility (section
4.3.3), and states that greater than 10 effective loads are possible
(sections 4.1.2 and 4.3.5). A compact layout with 10 or fewer loads is
just easier to make work without a lot of signal integrity design
effort.
It has sometimes been argued (and disputed) that it is the stub -- not
the connector itself -- that makes a slot like two effective loads. If
so, the slots at the electrical ends of the bus might count as one load
each.
PICMG passive PCI backplanes are governed by their own specification and
not just the PCI SIG's PCI Spec.
Regards,
Andy