Can you help me on a memory question? Suppose there\'s a virtual memory system w

Question

Can you help me on a memory question?

Suppose there's a virtual memory system with 32 bit physical and virtual addresses and a 4KB page size. Here's a few questions, and what I've gathered to be the answers.

- How many bits are needed for the offset part of the virtual address? I got 12 bits.

- how many bits are needed for the page number part of the virtual address? I got 20 bits.

- how many different page numbers does this system support? I got 2 ^ 20.

- if a page table entry takes up 4 bytes, how much space would a page table take up if it was stored in virtual memory? I got 2097152.

Are my answers right? Where did I go wrong, if I did?

Explanation / Answer

If the size of

Logical-address space is 2m, and

A page size is 2n addressing units (bytes or words),

then the high-order m - n bits of a logical address designate the page number,

and the n low-order bits designate the page offset.

In Your Question:
Logical Address : 232 i.e. (m=32)

Page Size: 4KB i.e. 212bytes (n=12)

Hence:
QUES: How many bits are needed for the offset part of the virtual address?

ANS: Page offset =

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