CONFIG_CPU_S3C6400 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
CONFIG_CPU_S3C6400 (not configurable)
configname: CONFIG_CPU_S3C6400
Linux Kernel Configuration
└─>Samsung S3C64XX (deprecated, see help)
└─>CPU_S3C6400
In linux kernel since version 2.6.31 (release Date: 2009-09-09)
Enable S3C6400 CPU support