CONFIG_6xx is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

512x/52xx/6xx/7xx/74xx/82xx/83xx/86xx

modulename: 6xx-suspend.ko

and/or

idle_6xx.ko

configname: CONFIG_6xx

Processor Type
└─>512x/52xx/6xx/7xx/74xx/82xx/83xx/86xx
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
source code:
/arch/powerpc/sysdev/
selects
CONFIG_PPC_FPU

is selected by
CONFIG_PPC_86xx