Compaq 108164-003 - ProLiant - 800 Integration Notes page 50

PCI Bus Numbering in a Microsoft Windows NT Environment
Reviewing the Test 2 Configuration – Addition of Two Controllers
Configuration B Test 2, illustrated in Table 15, provides an example of how the PCI BIOS
discovers new controller devices that were not present in the original Test 1 configuration and
how it assigns bus numbers during the discovery process. As in Test 1, the PCI BIOS moves
through the bus detection order looking for controller devices (not the slot numbers). In this
example, the PCI BIOS begins at the Host Bus and assigns bus 0 to the Primary Bus. Controllers
that do not contain a bridge receive 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 have a bridge so it receives
a bus assignment of bus 0. The PCI BIOS continues to search for the next device downstream on
the Primary Bus. Two bridged controllers were added to the configuration. The PCI BIOS upon
discovery of each controller assigns a bus number to the PCI bus on the bridged controller. Slot 4
now contains a SMART-2/P Drive Array Controller on bus 1 and slot 5 now contains a Dual
10/100TX PCI UTP Controller on bus 2.
With the addition of these two new controllers in the system, all other controllers that are
discovered by the PCI BIOS after slot 5 in the discovery process are now assigned a new bus
number. The SMART-2/SL Drive Array Controller in slot 6, a bridged device, is discovered next.
The PCI BIOS assigns bus 3 to the PCI bus on the controller, which changes the original bus
number assignment. This is also the last PCI controller discovered on the Primary Bus.
At this point, all bus number assignments on the Secondary Bus change when the PCI BIOS
discovery process continues. The Secondary Bus is assigned bus 4. The controllers downstream
on the Secondary Bus in slots 8 and 10 both contain bridges. Bus number assignments are made
to the PCI buses on these bridged controllers. The SMART-2/SL Drive Array controller in slot 8
is assigned bus 5 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.
Comparison of Test 1 to Test 2 - Configuration B
When you reboot the server and run the System Configuration utility to view the hardware
configuration changes, it displays slot and bus number assignments. Test 2 data was recorded and
compared to Test 1.
A side-by-side comparison of the slot configurations and bus numbers of each device in Test 1 to
the slot configurations and bus numbers of each device in Test 2, illustrates what bus numbers
were changed after modifications took place.
Slot Controller
Slot 3 Netelligent 10/100 TX (non-bridged)
Slot 4 SMART-2/P Drive Array (bridged)
Slot 5 Netelligent Dual 10/100 TX (bridged)
Slot 6 SMART-2/SL Drive Array (bridged)
Slot 7 Empty
Slot 8 SMART-2/SL Drive Array (bridged)
Slot 9 Empty
Slot 10 Netelligent Dual 10/100 TX (bridged)
Slot 11 Empty
13UK-1200A-WWEN
Test 1 Test 2 Bus Assignment
$ $
Bus 0 - No Change
$
Bus 1 - New
$
Bus 2 - New
$ $
Bus 1 to Bus 3 - Changed
N/A
$ $
Bus 3 to Bus 5 - Changed
N/A
$ $
Bus 4 to Bus 6 – Changed
N/A
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