CONFIG_SUN4 is not available for thedefaultarchitecture x86.
Result is shown for architecture sparc

Support for SUN4 machines (disables SUN4[CDM] support)

modulename: sun4setup.ko

configname: CONFIG_SUN4

Linux/SPARC Kernel Configuration
└─>General machine setup
└─>Support for SUN4 machines (disables SUN4[CDM] support)
In linux kernel since version 2.6.12  
Say Y here if, and only if, your machine is a sun4. Note that
a kernel compiled with this option will run only on sun4.
(And the current version will probably work only on sun4/330.)

source code:
depends
NOT CONFIG_SMP

is selected by
CONFIG_ATA