CONFIG_POWER4 is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

CONFIG_POWER4 (not configurable)

modulename: open_pic2.ko

and/or

idle_power4.ko

and/or

cpu_setup_power4.ko

configname: CONFIG_POWER4

Linux/PowerPC Kernel Configuration
└─>Processor support
└─>POWER4
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
source code:
arch/ppc/syslib/open_pic2.c
depends
CONFIG_PPC64 |
| CONFIG_PPC_BOOK3S

is selected by
CONFIG_PPC_PMAC64