CONFIG_CPU_TX49XX is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

R49XX

modulename: c-r4k.ko

and/or

dump_tlb.ko

and/or

r4k_fpu.ko

configname: CONFIG_CPU_TX49XX

CPU type
└─>R49XX
In linux kernel since version 2.6.12  
source code:
arch/mips/mm/


is selected by
CONFIG_TXX9_WDT