CONFIG_AMD_NB (not configurable)

modulename: amd_bus.ko

and/or

amd_nb.ko

configname: CONFIG_AMD_NB

Linux Kernel Configuration
└─>Bus options (PCI etc.)
└─>AMD_NB
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
source code:
arch/x86/pci/amd_bus.c

is selected by
CONFIG_GART_IOMMU