LBSC 690 - Information Technology
Fall 2003 - Section 0101
Assignment 1

This homework is due to the TA by email before the start of the second
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 computer system
that you might be considering buying:

Processor type:         Intel Pentium IV
Processor speed:        2 GHz
Hard drive:             30 GB, 10 ms access time
RAM:                    512 MB
Additional peripherals: CD-RW

1. If you buy some 640 MB write-once CD-R disks that can be written by
   the CD-RW drive, how many disks would you need to buy to back up a
   full hard drive once (assume no compression)?  At 7 cents per disk,
   how much would a full backup cost?  At 10 minutes per disk, how
   long would a full backup take?

Now. lets see how much stuff that hard drive can hold.  Assume you
have access to the following information stored for all 260 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.  

2. 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?

Now lets see how long it would take to read that much data off the
disk.  

3. 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 260 million people?  Could this be
   done in a second?  In a minute?  In an hour?  In a day?  In a month?
   In a year?

Assume for the sake of comparison that all of this data could fit in
RAM (it won't; you should convince yourself of that).  

4. How long would it take the processor to perform 260 million
   additions if it can perform one addition instruction for every two
   clock cycles (this means that 2 GHz equates to 1,000 MIPS)?  Could
   this be done in a second?  In a minute?  In an hour?  In a day?  In
   a month?  In a year?

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 come to class next week
ready to explain how virtual memory helps to accommodate this
mismatch.