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Sample Solution Written Exam in VLSI I - Integrated Systems ...

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Problem 3: Consider the data dependency graph <strong>in</strong> Fig. 7. The <strong>in</strong>put x[n] is real valued. Usef(x) = x 2 .x[n]c c c c0 1 2 3f(x)f(x) f(x) f(x)max max maxy[n]Figure 7: DDG(a) F<strong>in</strong>d a mathematical expression describ<strong>in</strong>g the DDG above.(1)(b) A possible hardware implementation is the isomorphic architecture. Describe how (2)this architecture is obta<strong>in</strong>ed from a DDG.(c) How can the ’max’ operations be reordered to shorten the critical path? Which (2)algebraic property of this function is used?(d) Commutativity and distributivity of multiplications allow to reduce the total numberof multiplications <strong>in</strong> this circuit. Draw the modified(3)DDG.Page 11 of 30<strong>VLSI</strong> I <strong>Exam</strong> Summer 2009

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