CS 110 Homework Assignment 4
Due: Tuesday, November 27, 9PM

  1. S&G, #8.2, pg 284 - 3 Points
    Explain the difference between internal and external fragmentation.
  2. S&G, #8.5, pg 285 - 5 Points
    Given memory partitions of 100K, 500K, 200K, 300K, and 600K (in order), how would each of the First-fit, Best-fit, and Worst-fit algorithms place processes of 212K, 417K, 122K, and 426K (in order)? Which algorithm makes the most efficient use of memory?
  3. S&G, #8.8, pg 285 - 5 points
    Consider a logical address space of eight pages of 1024 words each, mapped onto physical memory of 32 frames.
    1. How many bits are there in the logical address?
    2. How many bits are there in the physical address?
  4. S&G, #8.10, pg 285 - 5 points
    Consider a paging system with the page table stored in memory.
    • If a memory reference takes 200 nanoseconds, how long does a paged memory reference take?
    • If we add associative registers, and 75 percent of all page-table references are found in the associative registers, what is the effective memory reference time? (Assume that finding a page-table entry in the associative registers takes zero time, if the entry is there)
  5. S&G, #8.14, pg 286 - 3 points
    Explain why it is easier to share a reentrant module using segmentation that it is to do so when pure paging is used.
  6. Tanenbaum #3.5, pg 142. 3 Points
    A minicomputer uses the buddy system for memory management. Initially it has one block of 256k at address 0. After successive requests for 5k, 25k, 35k, and 20k come in how many blocks are left and what are their sizes and addresses?

Last modified November 8, 01 by mike@cs.hmc.edu