The system (HP DL145) has a PhoenixBIOS with an AMD Opteron Processor. Select the ''Advanced'' tab. In the ''Advanced'' window there is a:
''MCFG Table: [Enabled]''
This must be set to:
''MCFG Table: [Disabled]''
Otherwise, Linux will not see the PCI-X slots correctly.
One can use the lspci command to see if the PCI-X cards are found.