I needed to add a BARRIER between : set_entryhi(KSEG0+idx*0x2000); and tlb_write_indexed(); in local_flush_tlb_range() (tlb-r4k.c), otherwise I get a bootup failure: Kernel panic: Caught Machine Check exception - probably caused by multiple matching entries in the TLB. Malta 5kc didn't have this problem. Also, the call set_entryhi(KSEG0); doesn't seem necessary. Alice