Fa07 midterm 2-solutions - University of California,...

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Page 1/17 University of California, Berkeley College of Engineering Computer Science Division EECS Fall 2007 John Kubiatowicz Midterm II December 3 rd , 2007 CS162: Operating Systems and Systems Programming Your Name: SID Number: Circle the letters of CS162 Login First: a b c d e f g h I j k l m n o p q r s t u v w x y z Second: a b c d e f g h I j k l m n o p q r s t u v w x y z Discussion Section: General Information: This is a closed book exam. You are allowed 1 page of hand-written notes (both sides). You have 3 hours to complete as much of the exam as possible. Make sure to read all of the questions first, as some of the questions are substantially more time consuming. Write all of your answers directly on this paper. Make your answers as concise as possible. On programming questions, we will be looking for performance as well as correctness, so think through your answers carefully. If there is something about the questions that you believe is open to interpretation, please ask us about it! Problem Possible Score 1 20 2 25 3 20 4 35 Total
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CS 162 Fall 2007 Midterm Exam II December 3 rd , 2007 Page 2/17 [ This page left for π ] 3.141592653589793238462643383279502884197169399375105820974944
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CS 162 Fall 2007 Midterm Exam II December 3 rd , 2007 Page 3/17 Problem 1: True/False [20 pts] In the following, it is important that you EXPLAIN your answer in TWO SENTENCES OR LESS (Answers longer than this may not get credit!). Also, answers without an explanation GET NO CREDIT. Problem 1a[2pts]: The Clock Algorithm requires hardware support for a “use” bit in the PTE. True / False Explain: When a hardware use bit is not available, the PTEs can be set to invalid when they are unused, so that when the page is accessed, a trap will occur, and the operating system can set the use bit in software. Problem 1b[2pts]: The Aloha algorithm for broadcast networking permitted a new transmitter to interrupt a message that was already partially transmitted. True / False Explain: Yes, because Aloha sends blindly without checking to see if there are any ongoing communications (it relies on retransmissions after detecting garbled packets). Problem 1c[2pts]: Memory mapped I/O devices cannot be accessed by user-level threads. True / False Explain: Memory-mapped I/O is accomplished using load/store instructions to a special region of memory; a user-level thread can access this region if the user’s page table has a mapping for it. Problem 1d[2pts]: It is possible to make Remote Procedure Calls (RPCs) with integer arguments between clients that use big-endian integers and servers that use little-endian integers. True / False Explain: The marshalling/unmarshalling code of RPC will automatically convert between network and host byte orders, thus accommodating any combination of host byte orders.
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Fa07 midterm 2-solutions - University of California,...

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