CONFIG_PPC_PMAC64 is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

CONFIG_PPC_PMAC64 (not configurable)

configname: CONFIG_PPC_PMAC64

Linux Kernel Configuration
└─>PPC_PMAC64
In linux kernel since version 2.6.15 (release Date: 2006-01-02)