PCI Bus Numbering in a Microsoft Windows NT Environment

PCI Bus Numbering in a Microsoft Windows NT Environment 29
13UK-1200A-WWEN
Configuration C, ProLiant DL580
Table 10 is an example of a ProLiant DL580 server set up as an original Window NT server
configuration. All the controllers included in this configuration were installed in the server before
Windows NT was loaded on the system. Windows NT detected network controllers in the
original configuration (see Table 10) during the installation process. However, when the
configuration is modified in Test 2 (see Table 11), PCI bus renumbering does occur.
Configuration C: Test 1 – Initial Configuration
Table 10. PCI BIOS bus detection in a ProLiant DL580–before removing and inserting NICs
Bus
Detection
Order/
Controller
Discovery
Slot
Number
PCI Bridge/
Controller Type
- Test 1
Bus Number
Assignment
Description of PCI BIOS
Discovery Process
1st
Primary
Bus (0)
Host to PCI
Bridge
Bus 0
2nd Slot 6 Empty N/A
3rd
Secondary
Bus (2)
Host to PCI
Bridge
Bus 2
4th Slot 1 NC3131(bridged) Bus 3
5th Slot 2 Empty N/A
6th Slot 3 NC3131
(bridged)
Bus 4
7th
Tertiary
Bus (7)
Host to PCI
Bridge
Bus 7
8th Slot 4 Empty N/A
9th Slot 5 Empty N/A
The PCI BIOS assigns 0 to the
Primary Bus and continues
downstream with the controller
discovery.
Slot 6 is empty, no PCI bus number
assignment.
The PCI BIOS discovers the
Secondary Bus and assigns it bus
number 2.
NIC in slot 1 contains a PCI bridge
and the PCI BIOS increments the
PCI bus number to 3.
Slot 2 is empty, no PCI bus number
assignment.
Slot 3 contains a bridged NIC and
assumes a bus number of 4.
Finally, detection and assignment of
the Tertiary Bus occurs,
incrementing to 7.
Since both slots on the Tertiary Bus
are empty, a PCI bus number
assignment does not occur for these
slots.
Reviewing the Test 1 Configuration
Configuration C−Test 1, illustrated in Table 10, provides an example of how the PCI BIOS
discovers controller devices and assigns bus numbers during the discovery process. As the PCI
BIOS moves through the bus detection order it looks for controller devices (not the slot numbers).
In this example, the PCI BIOS begins at the Host Bus and moves downstream assigning bus
numbers starting at bus 0 on the Primary Bus. In this scenario, no PCI devices reside on the
Primary bus, so the discovery process continues to the Secondary Bus and assigns 2 as the bus
number. The NC3131 Fast Ethernet NIC is the first device detected. Since this controller contains
a PCI bridge, the bus number increments to 3. Slot 2 contains no device, so no bus number