The implementation of merged floating-point multiply-add operations can be optimized in many ways. For latency sensitive applications, our cascade design reduces the accumulation dependent latency by 2x over a fused design, at a cost of a 13% increase in non-accumulation dependent latency. A simple in-order execution model shows this design is superior in most applications, providing 12% average reduction in FP stalls, and improves performance by up to 6%. Simulations of superscalar out-of-order machines show 4% average improvement in CPI in 2-way machines and 4.6% in 4-way machines. The cascade design has the same area and energy budget as a traditional fused multiple-add FMA.
Real number models, which are computationally efficient analog functional models, are now indispensable in verifying complex mixed-signal systems on chip (SoCs); yet, creating and validating these models remain difficult. To remove this problem, we created a framework for building analog functional model templates. Each template covers a class of circuits (e.g., oscillators or amplifiers) and can generate functional models for any implementation of this circuit class, regardless of pin configurations, circuit topologies, and process technologies/corners. This ability to cover many implementations with one template allows one to create a "standard model template" library that covers all the basic analog building blocks used in mixed-signal SoCs. Like a digital standard cell library, this template library only contains the low-level building blocks. Models for more complex systems, such as a phase-locked loop, are constructed using a number of these models. Our template library also contains validation routines for each of the models, measuring the key performance parameters of the modeled function. These routines can also be used to drive the circuit-level implementation of this function, making it easy to update the parameters of the functional models to match their circuit implementations. We demonstrate the utility of our template library on several mixed-signal IPs integrated into an SoC. Using the proposed framework, designers can easily generate a working model of an analog functional block in a second and thus construct a complete mixed-signal IP model for the design exploration in less than a couple of hours, while it typically needs a few days when the models are manually written. The regeneration of the models to reflect the behaviors of real implementations can be seamlessly done in less half a day from the same template library. In addition to the vast improvement in model creation speed, the generated model from the template library is less error-prone by archiving designer's experience from previous mistakes to the template library.
A receiver targeting OC-48 (2.488 Gb/s) serial data link has been designed and integrated in a 0.8-/spl mu/m CMOS process. An experimental receiving front-end circuit demonstrates the viability of using multiple phased clocks to overcome the intrinsic gate-speed limitations in the demultiplexing (receiving) and multiplexing (transmitting) of serial data. To perform clock recovery, data is 3/spl times/ oversampled so that transitions can be detected to determine bit boundaries. The design of a transmitter for the high-speed serial data is also described. The complete transceiver occupies a die area of /spl sim/3/spl times/3 mm/sup 2/.
Abstract : This research focused on the design and development of scalable shared-memory machines, in particular, those using directory-based cache coherence. This research led to the design and fabrication of the machine - the Stanford DASH machine.
BackgroundThere are no analyses of citations to books on epidemiological and statistical methods in the biomedical literature. Such analyses may shed light on how concepts and methods changed while biomedical research evolved. Our aim was to analyze the number and time trends of citations received from biomedical articles by books on epidemiological and statistical methods, and related disciplines.Methods and FindingsThe data source was the Web of Science. The study books were published between 1957 and 2010. The first year of publication of the citing articles was 1945. We identified 125 books that received at least 25 citations. Books first published in 1980–1989 had the highest total and median number of citations per year. Nine of the 10 most cited texts focused on statistical methods. Hosmer & Lemeshow's Applied logistic regression received the highest number of citations and highest average annual rate. It was followed by books by Fleiss, Armitage, et al., Rothman, et al., and Kalbfleisch and Prentice. Fifth in citations per year was Sackett, et al., Evidence-based medicine. The rise of multivariate methods, clinical epidemiology, or nutritional epidemiology was reflected in the citation trends. Educational textbooks, practice-oriented books, books on epidemiological substantive knowledge, and on theory and health policies were much less cited. None of the 25 top-cited books had the theoretical or sociopolitical scope of works by Cochrane, McKeown, Rose, or Morris.ConclusionsBooks were mainly cited to reference methods. Books first published in the 1980s continue to be most influential. Older books on theory and policies were rooted in societal and general medical concerns, while the most modern books are almost purely on methods.
There is increasing concern that most current published research findings are false. The probability that a research claim is true may depend on study power and bias, the number of other studies on the same question, and, importantly, the ratio of true to no relationships among the relationships probed in each scientific field. In this framework, a research finding is less likely to be true when the studies conducted in a field are smaller; when effect sizes are smaller; when there is a greater number and lesser pre-selection of tested relationships; where there is greater flexibility in designs, definitions, outcomes, and analytical modes; when there is greater financial and other interest and prejudice; and when more teams are involved in a scientific field in chase of statistical significance. Simulations show that for most study designs and settings, it is more likely for a research claim to be false than true. Moreover, for many current scientific fields, claimed research findings may often be simply accurate measures of the prevailing bias. In this essay, I discuss the implications of these problems for the conduct and interpretation of research.
Understanding the AC current flowing through BGA package pins is critical to create accurate models of the power distribution network. We show that these currents can be experimentally measured by inserting small induction loops next to the vias carrying the pin currents. Small induction loops were constructed which gave a measurement upper cutoff frequency of 2 GHz, and a sensitivity of about 0.14 mV/mA/ns This system allowed us to measure currents with an average accuracy of about 10% and a dI/dt as small as 6 muA/ns with averaging when measuring calibrated test structures
