COS 318: Operating Systems, Fall 2013

Quiz 4: I/O and Communication

Due: 11:55pm, Wednesday, November 13

This quiz checks your understanding of the lectures and reading assignments. You may reference the textbook, lecture slides, and your notes. Online sites (e.g., Wikipedia) may also be consulted but you must cite them in your writeup.

Each question is worth three points. Please strive for clarity and brevity in your answers. Essay questions should require no more than one short paragraph.

Submit your answers by clicking the "submit" link on the lecture schedule page. Only online submissions will be accepted. Please use this template when preparing your answers, and submit a plain ASCII text file.

Questions:

  1. In the lecture, we discussed the basic steps of a disk DMA write (i.e., the interaction between the CPU and disk adaptor) with a simplified DMA hardware mechanism. Assuming the same simplified hardware, describe how a disk DMA read operation works.

  2. In class, we discussed indirect addressing for message passing and showed the example below:

    Producer/consumer

    1. Note that mailbox addressing is indirect in the example. Does the pseudo code work for:

      • A single producer and a single consumer.
      • A single producer and multiple consumers.
      • Multiple producers and multiple consumers.

    2. If we change the indirect addressing mechanism to direct addressing (sending to and receiving from processes directly), would the modified pseudocode work in the three cases above? Why or why not?