12. Consider a virtual memory system running on a RISCCPU. Page tables are not l

Question

12. Consider a virtual memory system running on a RISCCPU. Page tables are not locked in memory and may be swapped to disk. An lw (load word) instruction reads one data word from memory; the address is the sum of the value in a register and an immediate constant stored in the instruction itself. Neither machine instructions nor page-table entries nor data words can cross a page boundary. In the worst case, how many page faults could be generated as a result of the fetch, decode, and execution of an lw instruction? (A) 2 (B) 3 (C) 4 (D) 5 (E) 6

Explanation / Answer

Solution :

In the worst case, 4 page faults could be generated as a result of the fetch decode and execution of lw instruction. first page fault is for the page table, second for the instruction fetching, third page fault for the operand effective address calculation and fourth for load instruction execution i.e. reading data from memory.

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