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To: cswiger@mac.com
From: "M. Warner Losh" <imp@bsdimp.com>
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cc: freebsd-current@freebsd.org
cc: alex.wilkinson@dsto.defence.gov.au
Subject: Re: Transparent bridges (a. k. a. HUB-to-PCI bridges)?
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In message: <41A416E7.4030107@mac.com>
            Chuck Swiger <cswiger@mac.com> writes:
: > Can you please elaborate on the following .... please ;-\
: > 
: > 1. PCI bridges 
: >    - Host-PCI
: >    - PCI-PCI
: 
: A host-PCI bridge is typically part of the "southbridge" chip of modern 
: motherboards; on Intel motherboards this is also called the ICH chip, such as 
: the 82801AA/BA/CA/etc.  VIA Southbridges include the VT8233/8235/8237/etc.
: 
: A PCI-PCI bridge is commonly found on multifunction PCI cards, an example 
: would be the DEC 21151 chip found on various four-port NICs.

Newer laptops (and other machines) typically have a PCI PCI bridge
that all the builtin hardware lives behind.  Many, but not all, of
these bridges are transparent pci pci bridges, maning they act much
like a subtractively decoded bridge.

Warner