Quiz1 Answer 1

1
Quiz1 - Answer 1

• The CPI (Cycles Per Instruction) for the first
  program is the sum of the frequency of each
  instruction type multiplied by the instruction
  type0.177 0.634 0.1012 0.103 5.21
• For the second program the CPI is 1 as each and
  every instruction takes 1 cycle.
• The 1st instructions completes in 8ns, the 2nd in
  10ns, the 3rd in 12ns, and the 4th in 14ns. So
  the speedup is28ns/14ns 2.0
• 1000 instructions complete in 8ns 9992ns
  2006nsThe speedup is 7000ns/2006ns 3.5

Quiz1 - Answer 2
2
Quiz1 - Answer 3

• The instruction after beq cant be fetched until
  the result of the comparison is known. It might
  be add or it might be subi. This is called a
  control hazard.
• A solution is to stall the pipeline (not fetch
  more instructions) until the branch is resolved.
  Another solution is to predict the branch is
  taken and fetch the subi instruction. If the
  prediction is wrong ...
• The control line PCsrc, which controls which is
  the next instruction to fetch is dependent on
• The opcode of the instruction.
• The value of the ALU zero line (if a branch is
  being performed)
• The value of the Interrupt line.

Quiz1 - Answer 4