CDA3101-F11-HW5-KEY

CDA3101-F11-HW5-KEY - CDA 3101 Organization of Computer...

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CDA 3101 Organization of Computer Systems Fall 2011 Homework #5 (40 points total) Assigned: Wednesday 01 November 2011 Due: at the start of lecture on Friday 18 November 2011 This assignment has three parts. Please start each part on a new page . Print NEATLY and put your name and section number on each page . Show your work. Please scan or Xerox- copy your homework before turning it in, and staple all pages together with a metal staple. Part I. Pipelining 1. Short Answer (8 pts, 2 pt per item) Define the following (one sentence): 1.1. Pipeline (computing) -- a set of data processing elements connected sequentially, such that the output of the i th element is the input of the (i+1) st element. The elements of a pipeline are often executed in parallel, to effect the overlapping execution of multiple instructions with the same circuitry. 1.2. Forwarding (in a pipeline) – a mechanism (often a set of wires) that transmits results from one pipeline stage to other pipeline stages without memory access. Forwarding can help reduce processing latency and reduce the number of stalls when certain types of dependencies are present. 1.3. Virtual Memory – a methodology that uses disk memory as backing store for main memory, when a computer’s physical memory is smaller than the address space required by a program. 1.4. Cache - a component that transparently stores data so that future requests for that data can be served faster. The data that is stored within a cache might be values that have been computed earlier or duplicates of original values that are stored elsewhere. 2. Simple Problems (12 pts, 4 pt per problem, show all work for full credit ): 2.1. If a pipeline with N stages (one cycle per stage) processes a program P consisting of M instructions without stalls or exceptions, how many cycles are required to process P ? Answer: N cyc = M + ( N – 1), where ( N – 1) cycles are required to fill the pipeline. 2.2. If a pipeline with N stages (one cycle per stage) processes program P , which has M instructions, of which a fraction 0 < p < 1 throws an exception that causes the entire pipe to be flushed, how many cycles are required to process P ?
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CDA 3101 Organization of Computer Systems Fall 2011 Answer: When addressing a problem such as this, it helps to divide the problem up into sub-problems. For example, if we think of program P as being comprised of n subsequences of M i instructions that end with a
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This note was uploaded on 12/10/2011 for the course CDA 3101 taught by Professor Small during the Fall '08 term at University of Florida.

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CDA3101-F11-HW5-KEY - CDA 3101 Organization of Computer...

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