Compaq 108164-003 - ProLiant - 800 Integration Notes page 10

PCI Bus Numbering in a Microsoft Windows NT Environment
Triple-Peer PCI Bus – The Compaq ProLiant 8000 is an example of the triple-peer PCI
architecture. The PCI BIOS begins the discovery process at the Host Bus. In a triple-peer PCI bus
architecture the Primary Bus is the first bus detected and it is assigned bus 0. The PCI BIOS then
looks for PCI controllers in slots on the Primary Bus. PCI controllers detected without bridged
PCI buses are assigned bus 0, which is the number of the bus it is seated in. However, if a PCI
controller is detected with a bridged PCI device, the PCI BIOS increments the bus number to 1
and assigns that bus number to the PCI bus detected on the bridged controller. This discovery
process continues until all PCI controllers and controllers with bridged buses on the Primary Bus
are detected. The PCI BIOS then continues the discovery process on the Secondary Bus until all
PCI buses are detected, and then on to the Tertiary Bus until all PCI buses are detected.
The diagram in Table 4 is an example of the discovery process.
Table 4. Example of PCI bus number order of detection for ProLiant 8000 (a triple-peer system)
ProLiant 8000 PCI Server Architecture
PCI BIOS Discovery Process
! Host Bus
" Primary PCI Bus
! PCI Slot 1 – Pri Bus Empty
! PCI Slot 2 – Pri Bus Empty
! PCI Slot 3 – Pri Bus Empty
! PCI Slot 4 – Pri Bus Empty
" Secondary PCI Bus
! PCI Slot 5 – Sec Bus Empty
! PCI Slot 6 – Sec Bus Empty
! PCI Slot 7 – Sec Bus PCI Controller (no bridge)
! PCI Slot 8 – Sec Bus PCI Controller (integrated PCI bridge)
! PCI Slot 9 – Sec Bus Empty
" Tertiary PCI Bus
! PCI Slot 10 – Ter Bus PCI Controller (no bridge)
! PCI Slot 11 – Ter Bus PCI Controller (integrated PCI bridge)
End of bus
discovery
The "Additional Troubleshooting Tips" section of this document contains a matrix titled "Table
11. PCI Bus Number Order of Detection Matrix". This matrix lists the PCI Bus detection order
for several Compaq ProLiant servers.
In this scenario, PCI BIOS assigns the Primary Bus as bus 0. Since it detects no devices in the
Primary Bus, the discovery process continues to the Secondary Bus, assigned bus 6. The first PCI
controller detected downstream from the Secondary Bus does not contain a bridge, this controller
is assigned bus 6, the same as the Secondary PCI bus. The discovery process continues with bus
number assignments for other controllers on the Secondary Bus based on the order of detection.
Once again, if the PCI controller is a bridged PCI device, the bus number increments, if the PCI
controller is a non-bridged device then the controller is assigned the same number as the bus it is
seated in. After detection on the Secondary Bus completes, the Tertiary PCI Bus is assigned the
bus 13.
13UK-1200A-WWEN
Controller Bus Bus Number
Detection Order Assignment
First 0
Second 0
Third 0
Fourth 0
Fifth 0
Sixth 6
Seventh 6
Eighth 6
Ninth 6
Tenth 7
Tenth 6
Eleventh 13
Twelfth 13
Thirteenth 14
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