CompArch: the 4th Epoch Looms

1. CompArch: the 4th Epoch Looms Bob Colwell ISCA 2002

2. The 1st Three Epochs • 1960’s: Mainframes Roamed The Earth • Birth of instruction set architecture • 1970’s: Experimentation, Minis, Supers • “semantic gap”, caches, MP, langs, OSs • ’80’s & ’90’s: Microprocessors Rule • Perf is everything -> clock rate is everything, PC’s, www bob.colwell@attbi.com

3. The 4th Epoch Dawns • Technical Reasons • Approaching Si limits • Design complexity grows without bound • Market Reasons • No more “killer apps”, old PC good enough • Volume growth flattening -> commoditization • World Status • Hackers, viruses, worms, IT warfare • High tech economies wired to www bob.colwell@attbi.com

4. How to predict new epoch? • History best predictor of future • Behavioral interviewing • Glew’s ASC prophecy model • Accurate event + time + place • Sequential trends • Conditional if X costs $N, then trend Z will occur • ISCA extrapolations • My own guesses bob.colwell@attbi.com

5. In more ways than one “Accurate”…don’t count on it Available on many web sites The crystal ball with all its mystique and secrets is probably the best known method of divination for predicting the future... Crystal scrying is done in near to almost total darkness. bob.colwell@attbi.com

6. Computing, Then and Now1 30 years bob.colwell@attbi.com

7. Computing, Then and Now2 From “kids-in-new-toy-store” to …today. bob.colwell@attbi.com

8. 29 Years of ISCA • Extract session topics, all 29 yrs • Tally across ISCAs • Apply trending, extrapolate wildly Thanks Eugene Miya! bob.colwell@attbi.com

9. ISCA Topics Tallied • Interesting… • MP & interconnect are among highest • Cache, memory, CPU arch are high • Dataflow? Logic prog? • This chart does not reflect changes over time… bob.colwell@attbi.com

10. ISCA Topics vs Time • Strong, sustained interest • Caches, memory, CPU arch, performance • Early interest that waned • Dataflow, Logic programming, VLSI arch, pipelining (may be reviving!) • Rising stars • ILP, Branching, MT, power-aware, emerging tech • Never-were’s • Real-time, secure computing, embedded Now For Some Sequential Predictions… bob.colwell@attbi.com

11. ISCA Prediction 1: mop-up • Mop-up operations will continue • Incremental improvements are lucrative • Enormous intellectual energy applied to extremely difficult targets (memory latency, low code parallelism) for small gains • Why? User path-of-least-resistance usually wins • Process tech improvements carry architecture • Some real gains will be posted • MT, CMP bob.colwell@attbi.com

12. ISCA Prediction 2: branch out • Threats to cash cow will be rebuked • Power-aware computing is a start • Battery-life is even better • How to guarantee RT if CPU throttles on temp? • DVD movie players, audio players require this • Security • 1950’s -- TV ads told you not to leave car keys • Computer industry at that level of maturity bob.colwell@attbi.com

13. ISCA Prediction 3: leave home • New opportunities arise • CMOS-based Moore’s Law will end • Whomever repeats this exercise in 30 yrs will have lived through it • Economics will stop MLaw before tech limits do • Quantum, molecular, non-CMOS, nano, MEMS, Spintronics, optical • ISCA shows some openness to these • At least, judging by the accepted papers bob.colwell@attbi.com

14. Non-ISCA Prediction 4: new opportunities • Incremental progression leads to step-function changes • E.g., non-volatile storage capacity doubling every year • This will lead to entirely new products • Prediction: when people can carry everything about their own lives with them, they will • Every homework assignment, letters, old email, favorite articles, music, addresses, phone numbers • Carry downloadable user profile to all other devices • Music, movies…Hollywood, get over it bob.colwell@attbi.com

15. Prognostications • Linear extrapolation: 2012, Pentium 8 • 12GHz, 8-way CMP, 4-way MT, 100MB L4 cache on die, 20GB/s optical I/O, 250W, 2TB hard drive What will users do with this? • Sequential prophecy alternative A • What they do now. Somewhat faster. Commoditized. • Sequential prophecy alternative B • They won’t want them. They’ll want affordable, mobile, ubiquitous, secure computing based on huge local non-volatile storage with auto-backup • Comp Arch must anticipate both alternatives! bob.colwell@attbi.com

16. So What Should You Work On? • Can’t tell you what to design • Combine my predictions with yours • Try to intersect future at profitable spot • Guidelines? Those I’ve got. bob.colwell@attbi.com

17. 10 Hints for Chip Designers • Design systems, not chips Forces good questions about I/O, caching, SW, usage models, feature weighting per market • Design-for-100M units is 100 times harder than design-for-1M unit Know which one you’re targeting • Observe Golden Rule of Silicon: Who Ships Volume Wins Even the biggest Si companies forget this • If 100 apps, architect’s creation should bottleneck 100 different ways Balanced systems are the goal bob.colwell@attbi.com

18. I/O, Memory, Cache CPU An Unbalanced System bob.colwell@attbi.com

19. 10 Hints for Chip Designers • CompArch needs the FT community The more capable computers get, the more taken-for-granted they become, the more irritated users get if they fail, and the less they care about why • If you didn’t test it, it doesn’t work You are responsible for overall product Architects can prevent otherwise-unfindable bugs • Don’t Overemphasize the Quantifiable Performance not always more important than quality, reliability, simplicity This pendulum has swung too far bob.colwell@attbi.com

20. 10 Hints for Chip Designers • Undefined flags don’t mean don’t care Size of affected user decides issue • Adding new instructions is hard Removing old obsolete ones impossible • Economics rule, not technology VHS beat Beta…x86 outlived Alpha Don’t design until you understand why bob.colwell@attbi.com

21. And then there’s Blue Crystals Laundry detergent “New! Improved! Now with Blue Crystals!” Microprocessors now in that same consumer space Pentium MMX was marketed accordingly Remember dancing bunny suits? Slot 1 hologram vs Celeron bob.colwell@attbi.com Photos courtesy Intel Corp.

22. We hate Blue Crystals, but… Glenn Hinton, architect extraordinaire at Intel, Wilkes Award Winner ‘02 • Need to balance • Urge to do whatever sells • Urge to innovate • Both legitimate concerns Sea change in our industry ~1995 Dancing bunny person bob.colwell@attbi.com Photos courtesy Intel Corp.

23. A Ten-Year Plan Two Tasks • We must fix what we’ve made Easier to use, more dependable Safe, secure • Catch the 4th epoch wave Ruled by economics Driven by new implementation technologies bob.colwell@attbi.com

24. Example Fix: Mission Availability • Is computing system fulfilling its mission? • Web server’s job is to satisfy legitimate requests, not just pings/sec (DoS attacks) • Real world: human errors, malicious attacks, HW & SW failures • Promising avenues • Recovery-oriented computing (UCB, Stanford, Mills College) • Autonomic computing (IBM) bob.colwell@attbi.com

25. But There Be Dragons Here • Observation: OoO machines easily restarted Opportunity! • Justifiable • P6 retirement watchdog timer • Watches for fwd progress beyond longest latency • Arguable • Pentium 4 deadlock/livelock detectors • Scattered around core of uArch • Reason: perf tweaks cause rare lockups Real problem: complexity in pursuit of perf, compensated by more complexity in recovery bob.colwell@attbi.com

26. Half of what you know about computers will help you in the 4th epoch. 4th Epoch : 1st 3 :: www : PC bob.colwell@attbi.com