Compaq 108164-003 - ProLiant - 800 Integration Notes page 30

PCI Bus Numbering in a Microsoft Windows NT Environment
assignment occurs. The NC3131 Fast Ethernet NIC (a bridged device), residing in slot 3,
increments the bus number. The discovery process completes with the discovery of the Tertiary
Bus, assigning a bus number of 7. Since slots 4 and 5 comprising the Tertiary Bus are empty, no
bus number assignment occurs for these slots.
IMPORTANT: The controllers added to the server configuration in our tests were selected only
to illustrate how bus renumbering occurs. This example is not meant to be a recommended
configuration.
Configuration A – Test 2 – Removing and Adding NICs
The example in Table 11 illustrates the PCI BIOS discovery and bus number assignment process
in the same ProLiant DL580 server, resulting in the reordering of bus numbers from the original
configuration. When adding new network interface controllers (NIC) to a server, the slot used to
input the device is significant since network connectivity can be lost for existing NICs in lower
numbered slots. Fortunately, this state is only temporary because the NIC driver must be
reconfigured to accommodate the new NIC, at which time the bindings for the other NICs will be
rebuilt.
Table 11. PCI BIOS bus detection in a ProLiant DL580–after removing and adding NICs
Bus
Detection
Order/
Controller
Discovery
1st
2nd
3rd
4th
5th
6th
7th
8th
9th
*Bus number is different than previous configuration
13UK-1200A-WWEN
Slot PCI Bridge/
Number Controller Type
- Test 1
Primary Host to PCI
Bus (0) Bridge
Slot 6 Empty
Secondary Host to PCI
Bus (2) Bridge
Slot 1 NC3131(bridged)
Slot 2 NC3131(bridged)
Slot 3 NC3131(bridged)
Tertiary
Host to PCI
Bus (7)
Bridge
Slot 4 Empty
Slot 5 Empty
Bus Number Description of PCI BIOS
Assignment Discovery Process
The PCI BIOS assigns 0 to the
Bus 0 Primary Bus and continues
downstream with the controller
discovery.
N/A
Slot 6 is empty, no PCI bus number
assignment.
Bus 2
The PCI BIOS discovers the
Secondary Bus and assigns it bus
number 2.
Bus 3
NIC in slot 1 contains a PCI bridge
and the PCI BIOS increments the
Bus 4
PCI bus number to 3.
Slot 2 also contains a PCI bridge,
Bus 5*
making its PCI bus number
assignment 4.
Bus 7
Slot 3 contains a bridged NIC and
assumes a bus number of 5.
Finally, detection and assignment of
N/A
the Tertiary Bus occurs,
incrementing to 7.
N/A
Since both slots on the Tertiary Bus
are empty, a PCI bus number
assignment does not occur for these
slots.
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