Technical data

Installing Expansion Boards
8-7
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The bus scanning process is in a recursive loop. The following explains this
loop:
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If the server BIOS detects a PCI-to-PCI bridge chip (PPB) on the
current Bus N, the bus number of the PPB is assigned as N + 1.
The server BIOS does not scan the next device or slot on the
current bus (Bus N). Instead, it scans the first device of Bus N + 1
and, if the first device is not PPB, it then scans the second device of
Bus N + 1.
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If the first device of Bus N + 1 is PPB, the bus number of the PPB
on Bus N + 1 is assigned as Bus N + 2. Once a PPB is found, the
scan path goes to that PPB until no PPB is found again.
Afterwards, it moves to the next device.
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The bus scanning process is recursive until no additional PPB
devices are found. The server BIOS then scans the other devices
on the last found PPB, and then goes back to the upper level bus
and continues to scan other devices. Being recursive, the server
BIOS returns to Bus N.