1. Cost and Performance

2. Goal Understand involved in the design of computer systems
Previous lecture
Goal
Understand
Engineering methodology
Design techniques
Correctness criteria
Evaluation methods
Technology trends
involved in the design of computer systems

3. Cost Components

4. Chip Cost Chip cost is primarily a function of die area
increases much faster than linearly due to yield
going larger gives diminishing performance returns

5. Chip Cost Die Cost goes roughly with die area4
chip cost = Die cost Testing cost Packaging cost
Final test yield
Die cost = Wafer cost
Dies per Wafer * Die yield
Die Cost goes roughly with die area4

6. Real World Examples
Chip Metal Line Wafer Defect Area Dies/ Yield Die Cost layers width cost /cm2 mm2 wafer
386DX $ % $4
486DX $ % $12
PowerPC $ % $53
HP PA $ % $73
DEC Alpha $ % $149
SuperSPARC $ % $272
Pentium $ % $417
From “Estimating IC Manufacturing Costs”by Linley Gwennap, Microprocessor Report, August 2, 1993, p. 15

7. What is Relationship of Cost to Price?
Component Costs
Direct Costs (recurring costs): labor, purchasing, scrap, warranty
Gross Margin (nonrecurring costs): R&D, marketing, sales, equipment maintenance, rental, financing cost, pretax profits, taxes
Average Discount: volume discounts and/or retailer markup

8. Price vs. Cost
Figures 1.7 and 1.8

9. Performance Time to run the task Tasks per day, hour, week, sec, ns …
Seoul to Pusan
10 hours
1 hour
Speed
100 km/h
1000km/h
Passengers 5
100
Throughput
500
100,000
Sonata
Boeing 727
Time to run the task
Execution time, response time, latency
Tasks per day, hour, week, sec, ns …
Throughput, bandwidth

10. Performance and Execution Time
Execution time and performance are reciprocals
Execution Time(Y) Performance(X) =
Execution Time(X) Performance(Y)

11. Performance Terminology
“X is n% faster than Y” means:
Execution Time(Y) Performance(X) n
= =
Execution Time(X) Performance(Y)
n = 100(Performance(X) - Performance(Y))
Performance(Y)
n = 100(Execution Time(Y) - Execution Time(X))
Execution Time(X)
Example: Y takes 15 seconds to complete a task,
X takes 10 seconds. What % faster is X?

12. Benchmark Programs 1. Real programs - SPEC benchmarks
2. Kernels - Livermore Loops and Linpack
3. Toy benchmarks - Quicksort, etc
4. Synthetic benchmarks - Dhrystone and Whetstone

13. SPEC: System Performance Evaluation Cooperation
First Round 1989
10 programs yielding a single number
Second Round 1992
CINT92 (6 integer programs) and CFP92 (14 floating point programs)
Different compiler flags are allowed for different programs
Third Round 1995
CINT95 (8 integer programs) and CFP95 (10 floating point programs)
Same compiler flags for all programs of a given language
measures both execution time and throughput
Fourth Round scheduled to be completed by 1999

14. SPEC Results

15. SPEC Results

16. Other SPEC Benchmarks SFS97 - NFS Performance
Web96 - WWW Server Performance
HPC96 - High-end System Performance
APC, MBC, PLB, OPC, XPC - Graphics System Performance

17. Summarizing Performance
Arithmetic mean
Represents total execution time
Harmonic mean
Consistent independent of reference
Geometric mean

18. Amdahl's Law: assessing enhancement
Speedup due to enhancement E:
ExTime w/o E Performance w/ E
Speedup(E) = =
ExTime w/ E Performance w/o E
Suppose that enhancement E accelerates a fraction
Fractionenhanced of the task by a factor Speedupenhanced,
and the remainder of the task is unaffected.
What are the new execution time and the overall
speedup due to the enhancement?

19. Amdahl’s Law
ExTimenew = ExTimeold x (1 - Fractionenhanced) + Fractionenhanced
Speedupenhanced 1
ExTimeold
ExTimenew
Speedupoverall = =
(1 - Fractionenhanced) + Fractionenhanced
Speedupenhanced

20. What’s the implication of Amdahl’s law for computer architects?
Integer instructions
memory FP
instructions
others
After adding a pipelined integer instruction execution unit
and cache memory (with FP emulation)
Integer
instructions
memory
FP instructions
others

21. Aspects of CPU Performance
CPU time = Seconds = Instructions x Cycles x Seconds
Program Program Instruction Cycle
Inst Count CPI Clock Rate
Program X
Compiler X (X)
Inst. Set X X
Organization X X
Technology X