I have a P4080 system which is generating random exceptions. The exception is a program fault and the ESR indicates an illegal op-code. I did find that the instruction cache entry for this address was NULL. Infact, the entire way was all NULL although looking at that memory address should valid instructions. i have now disabled the instruction cache and also the data cache and i am still seeing the same fault. The fault occurs in random places and also at random times. I can execute the same code 100 times without fault and then get a series of faults all in different memory locations. However, the dumping memory at the location of SRR0 shows valid op-codes. Can anyone throw any light on what the problem maybe.