CONFIG_CPU_S3C6400 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
CONFIG_CPU_S3C6400 (not configurable)
modulename: s3c6400.ko
configname: CONFIG_CPU_S3C6400
Linux Kernel Configuration
└─>CPU_S3C6400
In linux kernel since version 2.6.31 (release Date: 2009-09-09)
Enable S3C6400 CPU support