CSE230-Quiz2-Ans

CSE230-Quiz2-Ans - bubbles as possible. ( Do NOT use any...

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Student Name:________________________________________ CSE230/EEE230 Quiz #2 Note: 1. The quiz is open book and open notes. No laptop usage allowed. 2 . There is only one problem, which is worth 75 points total. 3 . Your answers must be legible and organized. Given the following sequence of instructions to be executed using a pipelined implementation. Assume that the pipeline stalls due to any of the 3 classes of hazards (structural hazards, data hazards, and control/branch hazards). 1 lw $s0, 0($s1) 2 add $s3, $s0, $s2 3 sub $s4, $s5, $s6 4 beq $s3, $s4, Label 5 sub $s1 $s3, $s4 6 Label: add $s5, $s3, $s6 1) Specify all the hazards that may occur in this piece of code. Solution: Cycles Instructions 1 2 3 4 5 6 7 8 9 1 IF ID EX Mem WB 2 IF ID EX Mem WB 3 IF ID EX Mem WB 4 IF ID EX Mem WB 5 or 6 IF ID EX Mem WB Between 1 and 2, 2 and 4, 3 and 4, 3 and 5: Data Hazard 4: Control Hazard Between 1 and 4: Structure Hazard 2) Show how to avoid those hazards by adding as few
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Unformatted text preview: bubbles as possible. ( Do NOT use any other techniques such as forwarding .) After adding the necessary bubbles, how many clock cycles are required to complete the execution of this piece of code? Solution: (Shorthand: I=IF, D=ID, X=Ex, M=Mem,W=WB) 1 I D X M W 2 I D X M W 3 I D X M W Student Name:________________________________________ 4 I D X M W 5 or 6 I D X M W 6 * I D X M W Note: Instruction 2 cannot start 1 cycle earlier since it would result in a structural hazard (i.e., the M of instruction 1 would overlap with the I of instruction 2). 17 or 18 cycles depending on if the branch is taken. * If the previous instruction is 6 (the branch is taken), then this row is empty....
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This note was uploaded on 05/11/2010 for the course CSE/EEE CSE/EEE230 taught by Professor Baoxinli during the Fall '08 term at ASU.

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CSE230-Quiz2-Ans - bubbles as possible. ( Do NOT use any...

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