CONFIG_X86_SUMMIT is not available for thedefaultarchitecture x86.
Result is shown for architecture i386

Summit/EXA (IBM x440)

configname: CONFIG_X86_SUMMIT

Subarchitecture Type
└─>Summit/EXA (IBM x440)
In linux kernel since version 2.6.12  
This option is needed for IBM systems that use the Summit/EXA chipset.
In particular, it is needed for the x440.

If you don't have one of these computers, you should say N here.

depends
CONFIG_SMP