Transparent bridges (a. k. a. HUB-to-PCI bridges)?

[M. Warner Losh]

In message: <41A416E7.4030107 at mac.com>
            Chuck Swiger <cswiger at 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