CONFIG_SGI_IP28 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

SGI IP28 (Indigo2 R10k) (EXPERIMENTAL)

modulename: ip28-berr.ko

configname: CONFIG_SGI_IP28

System type
└─>SGI IP28 (Indigo2 R10k) (EXPERIMENTAL)
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
This is the SGI Indigo2 with R10000 processor. To compile a Linux
kernel that runs on these, say Y here.

source code:
arch/mips/sgi-ip22/ip28-berr.c

depends
CONFIG_EXPERIMENTAL