Question
Consider a VEX executing VLIW machine with the following characteristics: The machine supports 4 slots (4 wide machine) with the following resources: 2 memory units
Consider a VEX executing VLIW machine with the following characteristics:
The machine supports 4 slots (4 wide machine) with the following resources:
2 memory units each with a load latency of 3 cycles
2 integer-add/sub functional units with latency of 2 cycle
1 integer-multiply functional unit with latency of 4 cycles
Each functional unit in the machine is pipelined and can be issued a new operation at each cycle. However, results of an operation are only available after the latency of the
operation has passed.
Given the following Sequential VEX Code (a total of 16 instructions)
1. ldw $r1 = 4[$r10]
2. add $r2 = $r1, $r10
3. ldw $r3 = 8[$r10]
4. ldw $r5 = 12[$r20]
5. sub $r4 = $r3, $r2
6. ldw $r6 = 0[$r21]
7. add $r8 = $r20, 4
8. sub $r7 = $r23, $r22
9. mpy $r9 = $r8, $r5
10. ldw $r13 = 12[$r27]
11. ldw $r14 = 4[$r27]
12. mpy $r14 = $r13, $r14
13. add $r11 = $r7, $r6
14. ldw $r12 = $r11[$r9]
15. sub $r15 = $r14, 4
16. add $r16 = $r12, 10
Note: An instruction cannot be scheduled in a given slot unless all of its operands are available from other instructions on which it is dependent.
Q. Calculate the number of cycles it takes to execute the VLIW code.
Q. How many slots remain empty where no instruction could be scheduled? Provide a ratio of empty slots to the total number of slots present in the instruction schedule.
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