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From: Clemens Ladisch <clemens@ladisch.de>
Newsgroups: comp.os.linux.hardware
Subject: Re: Difference between PCIe host bridge and PCI-PCI bridge
Date: Sat, 3 Jun 2017 19:01:55 +0200
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Tan wrote:
> I would appreciate if someone explains the difference between PCIe host
> bridge and PCI-PCI bridge on Intel platforms.

PCI/PCI bridges are interfaces between two PCI buses.
The host bridge (or root complex) is the interface between the top-level
PCI bus and the CPU (the host).

> I found that PCI-PCI bridges have Header Type '1' while Host Bridge
> have header type '0'. As per my understanding, only non Bridge devices
> support header type '0'.

From the point of view of the PCI bus, the host is not visible as a PCI
device, so the device called "host bridge" is not actually a bridge.


Regards,
Clemens