CONFIG_CPU_SHX3 is not available for thedefaultarchitecture x86.
Result is shown for architecture sh

CONFIG_CPU_SHX3 (not configurable)

configname: CONFIG_CPU_SHX3

Linux/SuperH Kernel Configuration
└─>System type
└─>CPU_SHX3
In linux kernel since version 2.6.23 (release Date: 2007-10-09)