Midterm Exam, CSCI 312, Fall 2015

  1. Wombat architecture (a wombat instruction set reference is attached)
    1. [7 points] Describe the function of each of the six parts of the wombat CPU. Draw a diagram of the wombat CPU.
    2. The wombat CPU has a single register. How would the instruction set have to change if a second register was added?
      1. [4 points] What new functionality would such a change add to the CPU? Describe at least one new class of instruction the change would enable.
      2. [2 points] Describe a potential new instruction format, draw a diagram of this format labeling the parts.
      3. [2 points] Describe the impact of this format change on all instructions involving an address and at least one register. (One generalized discussion will do, you don't need to discuss each instruction)

  2. [3 points] One of the ideas in computer architecture is to "Make the common case fast". Give an example, using the wombat architecture, where "making the common case fast" will have an impact on performance.

  3. [3 points] A simple interpretation of CPI is that it is completely determined by the implementation of the hardware. Name and describe at least three other factors that influence CPI other than hardware.

  4. Two implementations of the same algorithm have the following characteristics:
    ImplementationCPI Instruction Count
    A 2.4 3.0 x 10 6
    B 2.5 2.6 x 10 6
    These two implementation are running on a processor with a 5MHz clock.
    1. [1 point] Comput the length of a single cycle of the clock in appropriate units. Show your work.
    2. [3 points] Compute the time required for each implementation. Show your work.
    3. [3 points] Compute and interpret the performance ratio of these two implementations.

  5. [4 points] Describe the role of abstraction in the CPU. Provide examples.

  6. [3 points] Give the truth table, circuit and equation for the logical or operation. Use notation employed in class.

    Over Please

     

     

  7. For a decoder
    1. [2 points] Describe the interface to a decoder.
    2. [2 points] Give the equations for the output of a 2 to 4 decoder.
    3. [2 points] Give a truth table for a 2 to 4 decoder.
    4. [2 points] Draw a circuit for a 2 to 4 decoder.

  8. An encoder will have at most one of the 2n input lines enabled. The address, in binary, of the input line is produced on the n output lines.
    1. [2 points] Draw a truth table to represent this device.
    2. [2 points] Derive equations for each of the outputs for this device.
    3. [2 points] Draw a circuit to implement this device, use only and, or, not gates.
    4. [1 point] Create an icon for this device, include i/o.