CONFIG_US3_FREQ is not available for thedefaultarchitecture x86.
Result is shown for architecture 64BIT or sparc

UltraSPARC-III CPU Frequency driver

modulename: us3_cpufreq.ko

configname: CONFIG_US3_FREQ

Linux Kernel Configuration
└─>Processor type and features
└─>UltraSPARC-III CPU Frequency driver
In linux kernel since version 2.6.12  
This adds the CPUFreq driver for UltraSPARC-III processors.

For details, take a look at Documentation/cpu-freq.

If in doubt, say N.

source code:
selects
CONFIG_CPU_FREQ_TABLE

depends
CONFIG_CPU_FREQ
CONFIG_SPARC64