Question

II. (a) An OS is using two-level paging to implement a 28-bit virtual address space per
process. The page size is 256-bytes, and the machine does not have a TLB. Explain the steps
involved in looking up the virtual address 0x03bf04d, when all pages are present in memory.
(2 points)

(b) For the system above, what is the maximum number of page faults that could be
generated in response to a memory access? (2 points)

Answer 1

(a)

8 bits needed for offset 256 bytes, 20 bits required for the VPN

Page table has 6 bits

Page directory has 14 bits

To look up the Operating System (OS) it will look the first 14 bits to find the physical address of the page in the table

Now Page Table Entry is found

Now you can find the physical address which then applies to the offset

(b)

Maximum number of page fault is one because the Page Table Entry(PTE) or Page Directory Entry(PDE) has a bit that stops it

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all the best