1. Computer Architecture
Exception Handling and Advanced Pipelining

2. Datapath with Controls to Handle Exceptions

3. Exception Handling Example
overflow exception

4. Exception Handling Example
start of exception handling routine

5. Advanced Pipelining Superpipelining Superscalar
Dynamic Pipeline Scheduling

6. Superpipelining IF-1 ID EX-1 EX-2 MEM WB IF-1 ID EX-1 EX-2 MEM WB IF-1

7. Superscalar IF ID EX MEM WB IF ID EX MEM WB IF ID EX MEM WB IF ID EX
ALU or Branch
Load or Store IF ID EX
MEM WB
ALU or Branch
Load or Store IF ID EX
MEM WB
ALU or Branch
Load or Store IF ID EX
MEM WB
ALU or Branch
Load or Store IF ID EX
MEM WB

8. Superscalar Pipeline

9. Simple Superscalar Code Scheduling
Loop: lw $t0, 0($s1) # $t0=array element
addu $t0, $t0, $s # add scalar in $s2
sw $t0, 0($s1) # store result
addi $s1, $s1, # decrement pointer
bne $s1, $zero, Loop # branch $s1!=0

10. Scheduled Code

11. Loop Unrolling

12. Dynamic Pipeline Scheduling
Example: Power PC 604, Pentium Pro, Alpha 21264, MIPS R10000

13. Dynamic Pipeline Scheduling
Overcome key performance limitations of in-order pipeline instruction execution
Structural hazard
Replicate pipelines
Data hazard
Execute instructions out of program order
Rename registers as needed
Control hazard
Execute instructions speculatively across branches

14. Dynamic Branch Prediction
One-bit prediction scheme
not-taken
taken
not-taken
predict not-taken
predict taken
taken
Problem : Loop case

15. Dynamic Branch Prediction
Two-bit prediction scheme
taken
not-taken
predict taken
predict taken
taken
not-taken
taken
not-taken
predict not-taken
predict not-taken
taken
not-taken

16. Summary Three major handles in pipelined implementation
Structural hazard
Data hazard
Control hazard
Advanced pipelining
Superpipelining (clock cycle time ↓)
Superscalar (CPI ↓, possibly < 1)
Dynamic pipeline scheduling
Structural hazard: resource replication
Data Hazard:
out-of-order execution
Register renaming
Control Hazard: speculative execution