1. Assembly line - start up
Chassis Axels Motor Seats Body
Start up waste t

2. Assembly line - stop 1. 2. 3. 4. 5. Chassis Axels Motor Seats Body
Chassis Axels Motor Seats Body
Nothing to do

3. Assembly line At start: final stations idle
At stop: start stations idle
5 “stages” for each car
Each car still takes 5 stages but...
... we produce one car each step

4. Assembly line  Time-set car Cycles instruction Without pipelining:
= 5
5 cycles
1 instr.
With pipelining
= 1
5 cycles
5 instr.

5. Pipelining T = Nq * CPI * Tc We can bring this But what
down to 1 determines this?
The slowest pipeline stage
“Rate determining step”

6. How we draw this? “At time t, pipeline step n works at the green car”

7. Pipeline is most efficient...
...when the work is equally shared
“critical path” delay same for each stage or
as close as possible

8. How do we break up a long critical path?
Insert flip - flops!

9. But - “no free lunch” Delay: 30 ns 10 ns Latency: 1 cycle 3 cycles
Also: The flip-flops have a cost!

10. Pipeline problem: Start-up waste Unexpected problem in a stage (stall)
No more orders (flush)

11. Zero ext. = =
Branch
logic A
ALU 4 B + = = 31 +
Sgn/Ze
extend