1. This exercise is intended to help you understand the relationship between forwarding, hazard detection and ISA design. Problems in this exercise refer to the following sequence of instructions and assume that it is executed on a 5-stage pipelined datapath add $s1, $s2, $s1 lw $s3, 4(Ss1) lw $s4, 0(Ss1) sub $s3, $54, $s3 sw $s3, 0($s1) addi $s6, $s4,-1 sw $s6, 4($s5) (a) If there is no forwarding or hazard detection, insert nops to ensure correct execution. Please indicate the result as in the following way. (15%) add $s1, $s2, $s1 | IF lw $s3, 4($s1) lw $s4, 0($s1) sub $s3, $s4, $s3 sw $s3, 0($s1) addi $s6, $s4,-1 sw $s6, 4($s5) | ID | EX ID IF | MEM | WB IF (b) Is it helpful if we can rearrange the MIPS code sequence to avoid nop insertion Note that the same execution results must be obtained. If it is possible, how to rearrange? If it is impossible, why? (10%) be asserted if we want to add forwarding path to solve all the hazards? (10%) figure on P81 to explain. Note that you have to define the state of the input (c) For the original code sequence, what kinds of hazard detection signals should (d) What kinds of signals are sent by the forwarding unit? Please use Fig. 4.60 or selection and its corresponding input port of the multiplexers. (10%) 1. This exercise is intended to help you understand the relationship between forwarding, hazard detection and ISA design. Problems in this exercise refer to the following sequence of instructions and assume that it is executed on a 5-stage pipelined datapath add $s1, $s2, $s1 lw $s3, 4(Ss1) lw $s4, 0(Ss1) sub $s3, $54, $s3 sw $s3, 0($s1) addi $s6, $s4,-1 sw $s6, 4($s5) (a) If there is no forwarding or hazard detection, insert nops to ensure correct execution. Please indicate the result as in the following way. (15%) add $s1, $s2, $s1 | IF lw $s3, 4($s1) lw $s4, 0($s1) sub $s3, $s4, $s3 sw $s3, 0($s1) addi $s6, $s4,-1 sw $s6, 4($s5) | ID | EX ID IF | MEM | WB IF (b) Is it helpful if we can rearrange the MIPS code sequence to avoid nop insertion Note that the same execution results must be obtained. If it is possible, how to rearrange? If it is impossible, why? (10%) be asserted if we want to add forwarding path to solve all the hazards? (10%) figure on P81 to explain. Note that you have to define the state of the input (c) For the original code sequence, what kinds of hazard detection signals should (d) What kinds of signals are sent by the forwarding unit? Please use Fig. 4.60 or selection and its corresponding input port of the multiplexers. (10%)
