CONFIG_CACHE_BOTH is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k

Both

configname: CONFIG_CACHE_BOTH

Split Cache Configuration
└─>Both
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
Split the ColdFire CPU cache, and use half as an instruction cache
and half as a data cache.