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 Celeron 900 (2.4GHz, 1MB L2 Cache, 800MHz FSB) Hard drive: 400GB, 7200 RPM, 12 ms access time RAM: 3GB 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. 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.
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