PCI Bus Numbering in a Microsoft Windows NT Environment

PCI Bus Numbering in a Microsoft Windows NT Environment 48
13UK-1200A-WWEN
Table 15. Test 1 – PCI BIOS bus detection in the ProLiant 6000 and 7000 servers
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
Bus Bridge
Bus 0
2nd Slot 1
(EISA)
N/A N/A
3rd Slot 2
(EISA)
N/A N/A
4th Slot 3 Netelligent
10/100 TX
Bus 0
5th Slot 4 Empty N/A
6th Slot 5 Empty N/A
7th Slot 6 SMART-2/SL
Drive Array
Bus 1
8th
Secondary
Bus (2)
Host to PCI
Bus bridge
Bus 2
9th Slot 7 Empty N/A
10th Slot 8 SMART-2/SL
Drive Array
Bus 3
11th Slot 9 Empty N/A
12th Slot 10 Netelligent
Dual 10/100
TX
Bus 4
13th Slot 11 Empty N/A
The PCI BIOS assigns 0 to the Primary Bus
and continues downstream with the
controller discovery.
The NIC in slot 3 does not contain a PCI
bridge device, it assumes the bus number of
the bus where it resides, which in this case
is bus 0. It is the first network controller
detected by the PCI BIOS.
Intelligent drive array controller with PCI
bridge is detected in slot 6. The PCI BIOS
increments the PCI number to bus 1 and
assigns it to the bridge on the controller.
The PCI BIOS discovers the Secondary Bus
and assigns it bus number 2.
Intelligent drive array controller (a PCI
bridge device) detected in slot 8. The PCI
BIOS increments the PCI bus number to 3
and assigns the bus number to the bridge
on the controller.
NIC in slot 10 contains a PCI bridge and the
PCI BIOS increments the PCI bus number
to 4.
Slot 11 is empty, no PCI bus number
assignment.
Reviewing the Test 1 Configuration – Initial Configuration
Configuration B−Test 1, illustrated in Table 15, 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. If the PCI BIOS detects a PCI device and it does
not contain a bridge it receives the bus number assignment of the bus on which it resides. In this
scenario, the Netelligent 10/100 TX Controller in slot 3 does not contain a bridge so it receives a
bus assignment of bus 0. The PCI BIOS continues to search for the next device on the Primary
Bus. The SMART-2/SL Drive Array Controller in slot 6, a bridged device, is discovered next.
The PCI BIOS assigns bus 1 to the PCI bus on the bridged controller. This is the last PCI
controller discovered on the Primary Bus.
At this point, the PCI BIOS discovery process continues to the Secondary Bus where it
increments the bus assignment to 2. The controllers detected later in the discovery order on the
Secondary Bus (slots 8 and 10) both contain PCI bridges. Bus number assignments are made to
the PCI buses on these controllers. The SMART-2/SL Drive Array controller in slot 8 is assigned
bus 3 and the Netelligent Dual 10/100 TX controller in slot 10 is assigned bus 4. Empty slots are
ignored, because they do not contain PCI devices.