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

[Charles Swiger]

On Nov 24, 2004, at 10:19 AM, John Baldwin wrote:
>> I've been wrong before, but please double-check diagrams like:
>>
>> http://www.intel.com/design/chipsets/850/pix/850_800.gif
>> http://www.viatech.com/en/products/chipsets/p4-series/pt880/
[ ... ]
> The northbridge is the host-pci bridge.  It contains a virtual PCI-PCI
> bridge/bus that represents AGP.

Agreed, although AGP is something of a special case.

> The chipset uses a propietary interconnect to the southbridge...

Such as VIA's V-link.

> ...such that the devices the north and south bridges connect
> to show up as one pci bus (bus 0).  You could build a system without a
> southbridge (just PCI-X bridges or some such) and it would still have a
> host-pci bridge.

You and Scott are correct.  pciconf claims that something like a 440BX 
northbridge (82443BX) contains both a HOST-PCI and a PCI-PCI bridge, 
whereas the PIIX4 southbridge (82371AB) has a PCI-ISA bridge, as well 
as ATA and the other things I'd mentioned.

I apologize if I confused the person I was trying to answer.

-- 
-Chuck