How do i find bits in virtual and physical address?

operating-system bits virtual-address-space page-size
user3233721 picture user3233721 · Apr 29, 2015 · Viewed 7.5k times · Source

The question is:

Consider a virtual address space of 256 pages with page size of 4KB, mapped onto a physical memory of 128 frames. How many total bits are required in the virtual address? How many total bits are required in the physical address?

I can't figure out how to number of frames is used with the number of pages to find the bits required.

Can someone explain the steps required to solve this problem?

Answer

user3344003 picture user3344003 · Apr 30, 2015

I'll bite, as much as I hate these theoretical problems with not practicable use:

There are 256 pages in the virtual address space. That means 8 bits are a required to identify a page.

The page size is 4096 bytes. It takes 12 bites to represent that many of bytes.

Therefore, you need 20 (8+12) bits for a virtual address.

There are 128 page frames. That requires 7 bits.

Therefore, you need 19 (7+12) bits for a physical address.

Related questions

How can I safely create a nested directory?

What is the most elegant way to check if the directory a file is going to be written to exists, and if not, create the directory using Python? Here is what I tried: import os file_path = "/my/directory/filename.…

Read More
What is the difference between a process and a thread?

What is the technical difference between a process and a thread? I get the feeling a word like 'process' is overused and there are also hardware and software threads. How about light-weight processes in languages like Erlang? Is there a …

Read More
Difference between binary semaphore and mutex

Is there any difference between a binary semaphore and mutex or are they essentially the same?

Read More