EECS 252 Graduate Computer ArchitectureLec 16 – Papers, MP Future Directions, and Midterm Review David PattersonElectrical Engineering and Computer SciencesUniversity of California, Berkeleyhttp://www.eecs.berkeley.edu/~pattrsnhttp://vlsi.cs.berkeley.edu/cs252-s06 1/3/2007 CS252 S06 Lec16 Review2Outline• ILP• Compiler techniques to increase ILP• Loop Unrolling• Static Branch Prediction• Dynamic Branch Prediction• Overcoming Data Hazards with Dynamic Scheduling• (Start) Tomasulo Algorithm• Conclusion1/3/2007 CS252 S06 Lec16 Review3Amdahl’s Law Paper• Gene Amdahl, "Validity of the Single Processor Approach to Achieving Large-Scale Computing Capabilities", AFIPS Conference Proceedings, (30), pp. 483-485, 1967.• How long is paper? • How much of it is Amdahl’s Law? • What other comments about parallelism besides Amdahl’s Law?1/3/2007 CS252 S06 Lec16 Review4Parallel Programmer Productivity• Lorin Hochstein et al "Parallel Programmer Productivity: A Case Study of Novice Parallel Programmers." International Conference for High Performance Computing, Networking and Storage (SC'05). Nov. 2005• What did they study?• What is argument that novice parallel programmers are a good target for High Performance Computing?• How can account for variability in talent between programmers?• What programmers studied?• What programming styles investigated? • How big multiprocessor?• How measure quality?• How measure cost?1/3/2007 CS252 S06 Lec16 Review5Parallel Programmer Productivity• Lorin Hochstein et al "Parallel Programmer Productivity: A Case Study of Novice Parallel Programmers." International Conference for High Performance Computing, Networking and Storage (SC'05). Nov. 2005• What hypotheses investigated?• What were results?• Assuming these results of programming productivity reflect the real world, what should architectures of the future do (or not do)?• How would you redesign the experiment they did? • What other metrics would be important to capture?• Role of Human Subject Experiments in Future of Computer Systems Evaluation? 1/3/2007 CS252 S06 Lec16 Review6CS 252 Administrivia• Monday March 20 Quiz 5-8 PM 405 Soda• Monday March 20 lecture – Q&A, problem sets with Archana• Wednesday March 22 no class: project meetings in 635 Soda• Spring Break March 27 – March 31• Chapter 5 Advanced Memory Hierarchy• Chapter 6 Storage• Interconnect Appendix1/3/2007 CS252 S06 Lec16 Review7High Level Message• Everything is changing • Old conventional wisdom is out• We DESPERATELY need a new architectural solution for microprocessors based on parallelism– My focus is “All purpose” computers vs. “single purpose”computers⇒ Each company gets to design one• Need to create a “watering hole” to bring everyone together to quickly find that solution– architects, language designers, application experts, numerical analysts, algorithm designers, programmers, …1/3/2007 CS252 S06 Lec16 Review8Outline• Part I: A New Agenda for Computer Architecture– Old Conventional Wisdom vs. New Conventional Wisdom– New Metrics for Success– Innovating at HW/SW interface without compilers– New Classification for Architectures and Apps• Part II: A “Watering Hole” for Parallel Systems– Research Accelerator for Multiple Processors• Conclusion1/3/2007 CS252 S06 Lec16 Review9• Old CW: Power is free, Transistors expensive• New CW: “Power wall” Power expensive, Xtors free (Can put more on chip than can afford to turn on)• Old: Multiplies are slow, Memory access is fast• New: “Memory wall” Memory slow, multiplies fast(200 clocks to DRAM memory, 4 clocks for FP multiply)• Old : Increasing Instruction Level Parallelism via compilers, innovation (Out-of-order, speculation, VLIW, …)• New CW: “ILP wall” diminishing returns on more ILP • New: Power Wall + Memory Wall + ILP Wall = Brick Wall– Old CW: Uniprocessor performance 2X / 1.5 yrs– New CW: Uniprocessor performance only 2X / 5 yrs?Conventional Wisdom (CW) in Computer Architecture1/3/2007 CS252 S06 Lec16 Review101101001000100001978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006Performance (vs. VAX-11/780)25%/year52%/year??%/yearUniprocessor Performance (SPECint)• VAX : 25%/year 1978 to 1986• RISC + x86: 52%/year 1986 to 2002• RISC + x86: ??%/year 2002 to presentFrom Hennessy and Patterson, Computer Architecture: A Quantitative Approach, 4th edition, 2006⇒ Sea change in chip design: multiple “cores” or processors per chip3X1/3/2007 CS252 S06 Lec16 Review11Sea Change in Chip Design• Intel 4004 (1971): 4-bit processor,2312 transistors, 0.4 MHz, 10 micron PMOS, 11 mm2 chip • Processor is the new transistor?• RISC II (1983): 32-bit, 5 stage pipeline, 40,760 transistors, 3 MHz, 3 micron NMOS, 60 mm2 chip• 125 mm2 chip, 0.065 micron CMOS = 2312 RISC II+FPU+Icache+Dcache– RISC II shrinks to ≈ 0.02 mm2at 65 nm– Caches via DRAM or 1 transistor SRAM (www.t-ram.com) ?– Proximity Communication via capacitive coupling at > 1 TB/s ?(Ivan Sutherland @ Sun / Berkeley)1/3/2007 CS252 S06 Lec16 Review12Déjà vu all over again?“… today’s processors … are nearing an impasse as technologies approach the speed of light..”David Mitchell, The Transputer: The Time Is Now (1989)• Transputer had bad timing (Uniprocessor performance↑)⇒ Procrastination rewarded: 2X seq. perf. / 1.5 years• “We are dedicating all of our future product development to multicore designs. … This is a sea change in computing”Paul Otellini, President, Intel (2005) • All microprocessor companies switch to MP (2X CPUs / 2 yrs)⇒ Procrastination penalized: 2X sequential perf. / 5 yrs32442Threads/chip4221Threads/Processor8222Processors/chipSun/’05IBM/’04Intel/’06AMD/’05Manufacturer/Year1/3/2007 CS252 S06 Lec16 Review13• Old CW: Since cannot know future programs, find set of old programs to evaluate designs of computers for the future– E.g., SPEC2006• What about parallel codes? – Few available, tied to old models, languages, architectures, …• New approach: Design computers of future for numerical methods important in future• Claim: key methods for next decade are 7 dwarves (+ a few), so design for them!– Representative codes may vary over time, but these numerical methods will be important for > 10 years21stCentury Computer Architecture1/3/2007 CS252 S06 Lec16 Review14High-end simulation in the
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