GATE - 2019 | Assume that in a certain computer, the virtual addresses are 64 bits long

Assume that in a certain computer, the virtual addresses are 64 bits long and the physical addresses are 48 bits long.
Posted on 02-02-2022

GATE - 2019 [Operating System]

Question:

Assume that in a certain computer, the virtual addresses are 64 bits long and the physical addresses are 48 bits long. The memory is word addressable. The page size is 8 kB and the word size is 4 bytes. The Translation Look-aside Buffer (TLB) in the address translation path has 128 valid entries. At most how many distinct virtual addresses can be translated without any TLB miss?

A

8×220

B

4×220

C

16×210

D

256×210

 

Solution 1:

A TLB has 128 valid entries.
So, it can refer to 27 pages.
Each page size is 8 kB & word is 4 bytes.
So, the total addresses of virtual address spaces that can be addressed

Assume that in a certain computer, the virtual addresses are 64 bits long and the physical addresses are 48 bits long.      

-------------------------------------------------------

Solution 2:

Number of words in a page 
= Page size / word size
= 8 KB / 4 B 
= 2 K
= 2 * 210 

Since TLB can hold 128 valid entries, therefore, TLB can translate

= 128 * number of words in page 
= 128 * 2 * 210
= 256 * 210 addresses with TLB hit 

So, option (D) is correct.

 

Thank You
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