w05-quiz3-solution

w05-quiz3-solution - ECE 30 Introduction to Computer...

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ECE 30 Introduction to Computer Engineering Quiz 3 February 16, 2005 Name Student ID Signature Your score out of 1 8 2 4 3 8 Total 20 You may only use the MIPS assembly instructions listed below. Do not use any other instructions! arithmetic add add addu add (unsigned) sub subtract subu subtract (unsigned) addi add immediate addiu add immediate (unsigned) mult multiply multu multiply (unsigned) div divide divu divide (unsigned) mfhi move from HI mflo move from LO logical and and or or srl shift right logical sll shift left logical
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1. Fast Adder Design (8 points) One approach to speed up the addition is to use the carry select scheme. The carry select adder (CSA) speculatively computes the results for both cases, C in = 1 and 0 , and selects the correct result after the correct value of C in becomes known. The CSA, thus, consists of two adders (one that assumes C in = 0 and the other that assumes C in = 1 ) plus a multiplexor. (a) (3 points) Design a 4-bit CSA using two 4-bit carry lookahead adders (CLA’s) and a 5-bit multiplexor. Complete the block diagram below. 5-bit MUX s b 2 b 1 b 0 b 3 b 4 y 2 y 1 y 0 y 3 y 4 a 2 a 1 a 0 a 3 a 4 if s = 0 , y = a if s = 1 , y = b 4-bit CLA a 0 a 1 a 2 b 0 b 1 b 2 c 0 s 2 s 1 s 0 c 4 a 3 b 3 s 3 4-bit CLA a 0 a 1 a 2 b 0 b 1 b 2 c 0 s 2 s 1 s 0 c 4 a 3 b 3 s 3 0
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This note was uploaded on 06/09/2008 for the course ECE 30 taught by Professor Gert during the Spring '08 term at UCSD.

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w05-quiz3-solution - ECE 30 Introduction to Computer...

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