University of Michigan Electrical Engineering and Computer Science 1 Top 5 Reasons Reliability is the Biggest Fallacy in Computer Architecture Research Scott Mahlke University of Michigan Thanks to Jason Blome, Shuguang Feng, and Shantanu Gupta for putting their research on reliable systems on hold to help with this presentation.

University of Michigan Electrical Engineering and Computer Science 2 Disclaimer Space shuttle, airplanes, etc. Cost is not an issue – use high degrees of redundancy Still a need for high reliability designs for mission critical systems *The speaker may not agree with this position I would like to convince you reliability is a fallacy for mainstream computer systems used in consumer/business electronics*

University of Michigan Electrical Engineering and Computer Science 3 Reason 1: It’s the Software, Stupid! “Mature OS can have an MTTF measured in months, while newer OS may crash every few days.” – Peter Chen: Reliability Hierarchies, 1999 HOT OS. Sources: [1] [2] A system-level approach for memory robustness, ICMTD05 [3] Lifetime Reliability: Towards an architectural solution, IEEE Micro 2005 [4]

University of Michigan Electrical Engineering and Computer Science 4 Hmm… My ATM Does Not Work

University of Michigan Electrical Engineering and Computer Science 5 Reason 2: Disposable Electronics “The average working life of a mobile phone is 7 years, but the average consumer changes their mobile every 11 months.

University of Michigan Electrical Engineering and Computer Science 6 PCs/Laptops Not Far Behind “Take-away something.” –

University of Michigan Electrical Engineering and Computer Science 7 Reason 3: A Transient Fault is About As Likely As …

University of Michigan Electrical Engineering and Computer Science 8 Reason 4: Does Anyone Care? Can a human identify errors in video, images, or sound? Glitches are accepted by the consumer (dropped cell calls) Natural redundancy and resiliency in software 100% reliable operation of hardware is not important or worth extra cost in many situations Which is flawed?

University of Michigan Electrical Engineering and Computer Science 9 Reason 5: This Problem is Better Solved Closer to the Circuit Level Intra-die variations in ILD thickness Error_L Error comparator RAZOR FF clk_del Main Flip-Flop clk Shadow Latch Q1 D1 0 1 Electromigration in copper Lower overhead Many designs benefit In-situ solutions naturally handle variation

University of Michigan Electrical Engineering and Computer Science 10 Some Hope? The bottom line What if we assume reliability is a looming problem. Then we need solutions that are: 1. Low overhead, high rate of return solutions Joint circuit/architectural techniques 2. Domain specific solutions – know thy customer 3. Reliability features provide other benefits Its not just a tax