LIS 7008 - Information Technologies
Spring 2012 - Section 01
Assignment 1

This homework is due to the instructor by email (attachment) before the beginning of 
next class session.  Partial credit may be awarded for an incorrect answer 
if you show your work.

First, lets look at a detailed specification for a Dell Inspiron 1525
laptop that you might be considering buying for $499:


CPU:              Intel Core 2 Duo T8100 (2.1 GHz, 2MB L2 Cache) 
Hard drive:       240GB, 5400 RPM, 12 ms access time
RAM:              2GB Shared Dual Channel DDR2 at 667MHz
Front-Side Bus:   533 MHz
Optical drive:    DVD+/-R/RW
Display:          Glossy, widescreen 15.4 inch display (1280x800)
Networking:       802.11g wireless Mini-card, 100 Mb/s Ethernet, 56kb/s v.92 modem
Battery:          28 Whr Lithium Ion
Operating System: Windows 7 Home Premium 64-bit


1. If you buy some 4.7GB write-once DVD-R disks that can be written by
   the DVD+/-R/RW drive, how many disks would you need to buy to back up a
   full hard drive once (assume no compression)?  At 30 cents per DVD-R disk,
   how much would a full backup cost?  At 10 minutes per DVD-R disk, how
   long would a full backup take?

2. Now, let's see how much stuff that hard drive can hold.  Assume you
   have access to the following information stored for all 306 million
   people in the United States

   Name:                40 characters 
   Phone Number:        10 characters
   Library Card Number: 9 characters
   Unpaid Fines:        one 4-byte number

   and that each character is stored in one byte.  

   Would all of this data fit on the hard drive of the computer
   described above?  If not, how big a hard drive would you need?  If
   so, what fraction of the disk would this fill?

3. Now lets see how long it would take to read that much data off the disk.  
   Assume that you access the data in a random order, and that you
   start a new disk access for each person.  How long would it take to
   add up the library fines for all 306 million people?  Could this be
   done in a second?  In a minute?  In an hour?  In a day?  In a month?
   In a year?

4. Assume for the sake of comparison that all of this data could fit in
   RAM (it won't; you should convince yourself of that).  
   How long would it take the processor to perform 306 million
   additions if it can perform one addition instruction for every two
   clock cycles (this means that 2.0 GHz equates to 1,000 MIPS because 
   2.0 GHz is 2,000 million cycles)?  Could this be done in a second?  
   In a minute?  In an hour?  In a day?  In a month?  In a year?
   Note for this question, you are not required to calculate the time for 
   transfering the data from RAM to CPU. Also note that Core 2 Duo has two CPUs.

From these answers, you should be able to conclude that the processor
is faster than the hard drive.  Review your notes and read the section
in the book about "virtual memory," and then you should be able to
explain how virtual memory helps to accommodate this mismatch.

Grading rubric:

     Each question is worth 25 points. For each question, points are to be deducted according to the type of mistakes. Typical mistake types are shown below. Atypical mistake types will be evaulated seperately.

• -0: approximate result due to minor math mistake.
• -1~-2: wrong result due to pure math mistake (such as 10x20=120).
• -5: formula mistake (such as being confused with multiplication and division, wrong units in result).
• -5: minor conceptual mistake (such as being confused with number of CPUs).
• -10~-20: medium to big conceptual mistake (such as being confused with disk and CPU).
• -20~-25: confusing calculation process (such as giving multiple answers to a question, hard-to-follow calculation process).
• -25: wrong answer to any question without showing calculation process.

Useful resources:

• How to Calculate MIPS Rating