CS439: Principles of Computer Systems

Discussion Section 6 Problem Set

Due in Section on Friday, March 7, 2025

The problem set must be completed before section and brought to section. To ensure that your problem set is turned in correctly and that you receive credit for discussion section, you must follow these guidelines exactly.

Include the following header at the top of your file:

Discussion Section Problem Set #:
Student Name:
EID:

You may either type your answers or write them by hand, but you must have a copy with you in discussion section.

In discussion section, your TA will check that you made a good effort on the problem set, you are participating in the discussions in section, and you are ready and able to answer when called upon. If all of those are true, you will receive credit for discussion section that day. Note that a "good effort" on the problem set includes that all answers are in words unique to you and not copied from anywhere else, including the slide deck.

Pages have (at least) the following three bits associated with them: the resident bit, the clock/reference bit, and the dirty bit. Describe each bit and its use.
What is the difference between global and local page replacement policies? Name a disadvantage of each.
What is the TLB (Translation Lookaside Buffer)? What issue does it try to solve? how does it solve that issue?
Consider a program with seven virtual pages numbered from 0 to 6 references its pages in the order:

0 1 3 6 2 4 5 2 5 0 3 1 2 5 4 1 0

Using clock page replacement algorithm with 4 frames and assuming demand paging, compute the number of page faults and show the state of frames (pages in frames and value of clock bit) after each page access.
Consider a two-level paging system with 256 pages and a page size of 256 bytes. The system has 1024 bytes of physical memory and is byte addressable. Assume the first-level page table holds 8 entries.
1. How many bits are in a physical address?
2. How many bits of the virtual address represent the first-level page table?
3. How many bits of the virtual address represent the second-level page table?
4. How many bits are in the complete virtual address?
5. What size are the page frames?