CONFIG_EMBEDDED6xx is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Embedded 6xx/7xx/7xxx-based board

configname: CONFIG_EMBEDDED6xx

Machine type
└─>Embedded 6xx/7xx/7xxx-based board
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
depends
CONFIG_BROKEN
CONFIG_PPC32 or CONFIG_6xx or CONFIG_BROKEN_ON_SMP or CONFIG_PPC_BOOK3S_32