gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseSize

This value is used to set the size of PCI express hierarchy. The default is 256 MB.
PCI Express Base Size.

PCD Information

Name	Token Space	Token number	Data Type	Default Value
PcdPciExpressBaseSize	gEfiMdePkgTokenSpaceGuid	0x0000000f	UINT64	0x10000000