Question

3. Virtual Memory (20 points) An ISA supports an 8 bit, byte-addressable virtual address space. The corresponding physical memory has only 256 bytes. Each page contains 32 bytes. A simple, one-level translation scheme is used and the page table resides in physical memory. The initial contents of the frames of physical memory are shown below. VALUE address size 8 bit byte addressable each byte of addressing type memory has its own address 32 B page size physical memory size 256 B Physical Page Contents FRAME (PHYSICAL PAGE) NUMBER FRAME CONTENTS 0 Empty Page 7 Page 1 3 Page 4 Empty 5 Page 3 Empty Page Table Questions A three-entry TLB that uses Least Recently-Used (LRU) replacement is added to this system. Initially, this TLB contains the entries for pages 3, 4, and 7. INITIAL TLB LRU PHYSICAL PAGE TAG (VPN) 4 3

Answer 1

3. A TLB misses /page faults:

LRU	TLB(VPN)	PHYSICAL PAGE #
?	3	5
?	4	3
?	7	1
3	3	5
7	7	1
1	1	3
4	4	5
10	10	1
10	10	1
7	7	3
11	11	5
11	11	5
7	7	3
8	8	1
10	10	5
8	8	1
7	7	3
12	12	5
9	9	1

                                                                                                   

8 , 10, 8 , 1, 12 , 9

TLB Hit Ratio: total repeated sequence /Total Number of Sequence= 4/16=0.22 (22.22% in terms of percentage)

TLB Hits: 3, 7, 4

Page Faults: 1,4,10, 11, 8, 12, 9

3. B Final TLB:

LRU	TLB(VPN)	PHYSICAL PAGE #
7	7	3
12	12	5
9	9	1

3. C Physical Frame Contents are

FRAME(PHYSICAL PAGE ) NUMBER	FRAME CONTENTS
0	Empty
1	9
2	1
3	7
4	Empty
5	12
6	Empty
7	Page Table