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

CONFIG_POWER4 (not configurable)

modulename: idle_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/powerpc/kernel/
depends
CONFIG_PPC64 |
| CONFIG_PPC_BOOK3S