Computer Science 322
Operating Systems

• Announcements
• Final project proposals and discussions
• Lecture assignment recap
• Working sets and Lab 6
• Memory management topics to read about
  • The other major approach: Segmentation
    • like paging, but with variable-sized segments instead of fixed-size frames
    • allocate segments according to logical breakdown of memory usage
    • segment table requires base and offset
    • external fragmentation can be a problem (as with the contiguous allocation approach)
  • Combinations of Segmentation and Paging
    • Intel Pentium memory hardware
      • Lots of details in IA-32 Intel Architecture Software Developer's Manual, Volume 3: System Programming Guide, available in shared area. Don't print it - it's over 800 pages. Memory management is described in great detail in Chapter 3.
      • Better: excerpt from newest Tanenbaum OS text (see handout).
    • FreeBSD approach
• Disks and disk structures
  • disk is arranged into cylinders, divided into sectors, which contain blocks
  • this arrangement is the drive geometry
  • hard to determine the real values in modern disks
  • access: line up read/write head over desired block
  • access time
    • seek time - time to move the read/write head
    • rotational latency - time to get the correct block under the read/write head

Due at the start of class, Wednesday, April 14.

Please submit answers to these questions either as a hard copy (typeset or handwritten are OK) or by email to jteresco AT mtholyoke.edu by the start of class. We will discuss these questions at the start of class, so no late submissions are accepted.

1. SG&G Exercise 9.21, p. 412-413
2. SG&G Exercise 9.24, p. 413
3. SG&G Exercise 9.32, p. 415