CONFIG_CPU_TX39XX is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

R39XX

modulename: c-tx39.ko

and/or

r3k_dump_tlb.ko

and/or

r2300_fpu.ko

configname: CONFIG_CPU_TX39XX

CPU type
└─>R39XX
In linux kernel since version 2.6.12  
source code:
arch/mips/mm/


is selected by
CONFIG_TXX9_WDT