# Andrew S. Tanenbaum (OS) Edition 4 Exercise 3 Question 9 (Page No. 255)

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What kind of hardware support is needed for a paged virtual memory to work?

An MMU is needed to map virtual pages to the physical pages.

## Related questions

1
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Virtual memory provides a mechanism for isolating one process from another. What memory management difficulties would be involved in allowing two operating systems to run concurrently? How might these difficulties be addressed?
Suppose that a machine has $438-bit$ virtual addresses and $32-bit$ physical addresses. What is the main advantage of a multilevel page table over a single-level one? With a two-level page table, $16-KB$ pages, and $4-byte$ entries, how many bits should be allocated for the top-level page table field and how many for the next level page table field? Explain.
Suppose that a machine has $48-bit$ virtual addresses and $32-bit$ physical addresses. If pages are $4\: KB$, how many entries are in the page table if it has only a single level? Explain. Suppose this same system has a $TLB$ (Translation Lookaside Buffer ... and it sequentially reads long integer elements from an array that spans thousands of pages. How effective will the $TLB$ be for this case?