Question

Given a system with 512G bytes of address space per process, 2G bytes of physical memory, and pages of size 2K bytes. How bits are needed to specify the offset?

Select one:

a. 39

b. 28

c. 11

d. 20

Given a system with 4M bytes of address space per process, 8M bytes of physical memory, pages of size 8K bytes, and page table entries of 4 bytes. How many entries can fit in one page?

Select one:

a. 8K

b. 2K

c. 4

d. 1K

Answer 1

Solution:

(1)

Given,

=>Logical address space size = 512 GB

=>Physical address space size = 2 GB

=>Page size = 2 KB

The answer will be an option,

(c) 11

Explanation:

Logical address:

Page number

Page offset

                                                                             11 bits

Physical address:

Frame number

Frame offset

                                                                             11 bits

Calculating number of bits for offset:

=>We know that frame size = page size and number of bits required for page offset and frame offset will be equal.

=>Number of bits required for page offset = log₂(page size in bytes)

=>Number of bits required for page offset = log₂(2 KB)

=>Number of bits required for page offset = log₂(2*2^10 B) as 1 KB = 2^10 B

=>Number of bits required for page offset = log₂(2^11)

=>Number of bits required for page offset = 11 bits

=>Number of bits required for frame offset = 11 bits

=>Hence option (c) is correct and other options are incorrect.

(2)

Given,

=>Logical address space size = 4 MB

=>Physical address space size = 8 MB

=>Page size = 8 KB

=>Page entry size = 4 bytes

The answer will be an option,

(b) 2k

Explanation:

Calculating number of entries in 1 page:

=>Number of entries in one page = page size/entry size

=>Number of entries in one page = 8 KB/4 B

=>Number of entries in one page = 8*2^10 B/4 B as 1 KB = 2^10 B

=>Number of entries in one page = 2^13 B/2^2 B

=>Number of entries in one page = 2^11

=>Number of entries in one page = 2*2^10

=>Number of entries in one page = 2 K as 1 K = 2^10

=>Hence option (b) is correct and other options are incorrect.

I have explained each and every part with the help of statements attached to it.