Power calculation for transistor operation

1. Power calculation for transistor operation • What will cause power consumption to increase? CS2710 Computer Organization

2. Measuring the current used by the Atmegamicroprocessor shows a linear relationship Note: V=5v for in this case CS2710 Computer Organization

3. What effect does increasing voltage to a microprocessor have on power? On speed? Below around 2.5v (for this microprocessor), the transistors simply stop working CS2710 Computer Organization

4. The Power Wall: Why haven’t clock rates continued to increase at historical rates? CS2710 Computer Organization

5. Manufacturers have turned to multi-core architectures to bypass the Power Wall Clock speed decrease, but overall performanceincrease CS2710 Computer Organization

6. Benchmarking Explain the SPEC benchmarks. Define Amdahl's law Define MIPS

7. Amdahl’s Law (p51) • The performance enhancement possible with a given improvement is limited by the amount that the improved feature is used CS2710 Computer Organization

8. Amdahl’s Law Applied • A Program spends 40 seconds performing network transfers and 60 seconds generating reports. • Suppose we could rewrite the report generatorto make it more efficient. • What improvement in performance in the report generator would be necessary to increase the overall speed of the program by a factor of 2? • How about by a factor of 3? CS2710 Computer Organization

9. A Performance Metric: MIPS Units: millions of instructions per second CS2710 Computer Organization

10. Issues with MIPS metrics • Measuresinstruction execution rate, but doesn’t consider the complexity of the instructions performed • Average instruction complexity varies between programs executing on a single computer • Different microprocessors implement instructions of differing complexities • MIPS may vary independently from performance • We cannot compare computers with different instruction sets using MIPS! CS2710 Computer Organization

11. Benchmarking: How do you decide which computer to buy? CS2710 Computer Organization

12. SPEC Benchmark • A set of programs used to measure performance • Supposedly typical of actual workload • Standard Performance Evaluation Corp (SPEC) • Develops benchmarks for CPU, I/O, Web, … • SPEC CPU2006 • Elapsed time to execute a selection of programs • Negligible I/O, so focuses on CPU performance • Normalize relative to reference machine • Summarize as geometric mean of performance ratios • CINT2006 (integer) and CFP2006 (floating-point) CS2710 Computer Organization

13. Geometric vs. Arithmetic Mean • Arithmetic mean: • Geometric mean: CS2710 Computer Organization

14. Which computer has better overall performance? CS2710 Computer Organization

15. Which computer has better overall performance? A is fastest via Arithmetic mean. A and B are tied via Geometric mean. Geometric mean is the appropriate mean when the ranges of the values being compared vary significantly. CS2710 Computer Organization

16. Benchmarking often computes performance relative to a standard reference Let’s say A is the “reference” computer. We adjust all performance values by dividing each value by the reference computer’s value. In this example, we divide all results for Program 2 by the reference computer’s performance value of 1000, giving: Scaling the results in this manner is called normalization. Note that no normalization was needed for Program 1 sincethe reference computer’s value was already 1. CS2710 Computer Organization

17. Arithmetic and Geometric means based on the normalized values: Now C is fastest via Arithmetic mean! A and B are still tied via Geometric mean. CS2710 Computer Organization

18. Now consider computer B to be the “reference” computer and normalize A and C w.r.t. B Now A is fastest via Arithmetic mean! A and B are still tied via Geometric mean. The Geometric mean is consistent regardless of normalization! CS2710 Computer Organization

19. The SPECjvm2008 application • SPECjvm2008 is a benchmark suite for measuring the performance of a Java Runtime Environment (JRE), containing several real life applications and benchmarks focusing on core java functionality. • The SPECjvm2008 workload mimics a variety of common general purpose application computations.  CS2710 Computer Organization

20. CINT2006 integer performance benchmarks for the OpteronX4 2356 • Highlight the high cache misses of a few, and how this impacts the overall performance • Highlight how different apps might be useful for different teams CS2710 Computer Organization

21. SPEC and power: ssj_ops(server-side java operations/sec) • Power consumption of server at different workload levels • Performance: ssj_ops/sec • Power: Watts (Joules/sec) CS2710 Computer Organization

22. A Power benchmark: SPEC Power versus loadSPECpower_ssj2008 for X4 CS2710 Computer Organization

23. Low power at low usage? No! • Look back at X4 power benchmark • At 100% load: 295W • At 50% load: 246W (83%) • At 10% load: 180W (61%) • Google data center • Mostly operates at 10% – 50% load • At 100% load less than 1% of the time • Future research/development: Design processors to make power proportional to load CS2710 Computer Organization