Dear all: When I read mips spec there is an exception called MCheck and my questions are: 1. Does this exception only happen on write? 2. The spec says this exception happens when following conditions matched: a. Existing Page Valid Bit = 1 b. Written Page Valid Bit = 1 what is the correct definition of "Existing Page" and "Written Page"? I guess the definition of "Written Page" is teh PFN we get from TLB. But what is "Existing Page"? 3. I google a paragraph which discuss about this exception, http://www.spinics.net/lists/mips/msg19804.html But I cannot find the reason why it happened from the log. The entries in TLB seems fine. BTW, where I can find kernel 1. first time fill Page blobal directory 2. handle a. tlb refill, invalid and modified? appreciate your help, miloody