Compaq 307560-001 PCI Bus Numbering in a Microsoft Windows NT Environment - Page 10

PCI Bus Numbering in a Microsoft Windows NT Environment 10 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 Controller Bus Detection Order First Second Third Fourth Fifth Sixth Seventh Eighth Ninth Tenth Tenth Eleventh Twelfth Thirteenth Bus Number Assignment 0 0 0 0 0 6 6 6 6 7 6 13 13 14 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