2397835
Speed clustering of integrated circuits
Experimental data on 0.18 /spl mu/ test chips shows strong evidence of clustering of speeds of neighboring dies on a wafer. This clustering phenomenon is utilized to develop techniques for predicting the speed of a part from the speeds of three or more of its neighbors. On-chip processor monitors are used to further improve the prediction accuracy of these techniques. Experimental data demonstrates both the effectiveness of these prediction schemes and the possibility of applying of them to reduce the cost of speed binning.
16114497
Scan synthesis for one-hot signals
Tri-state buses and pass transistor logic are used in many complex applications to achieve high performance and small area. Such circuits often contain logic requiring one-hot signals. In a scan-based design, one-hot values on these signals may not be maintained during the scan-in and scan-out operations. Also, the presence of faults, the existence of don't care conditions and the use of random patterns for testing the circuit in a scan or BIST environment may lead to non-one-hot values on these one hot signals, resulting in abnormal circuit behavior and possible circuit damage. In this paper, we present new techniques for synthesizing scan-based designs so that one-hot values are maintained on the one-hot signals during all modes of operation. One of our synthesis techniques often generates designs with no area overhead-the designs are smaller than those that do not ensure safe scan operation. In addition, we propose a scan path design that has no performance overhead during the normal mode of operation and ensures that only valid states appear on the bistables during test mode, thus guaranteeing safe scan operations.
18607273
X-tolerant test response compaction
Larger, denser designs lead to more defects; higher quality requirements and new test methods lead to an explosion in test data volume. Test compression technique attempt to do more testing with fewer bits. This article summarizes one such method, X compact which addresses how unknowns the bane of compression and logic BIST techniques are eliminated. DFT engineers must spend serious effort to minimize Xs in future designs. It is impossible to eliminate all Xs. X-tolerant response compactors are necessary for tolerating residual Xs to enable massive compaction with practically no impact on test quality. X-compactors are mainly useful for test compression purposes and provide up to 80 times the test response compaction of traditional scan. X-tolerant signature analyzers extend the X-compact concept to incorporate time compaction, thereby tolerating thousands of Xs and reducing test response data volume by 50 to 2,000 times relative to traditional scan. These signature analyzers are extremely beneficial for BIST because Xs can easily corrupt traditional MISR-based BIST signature analyzers. X-tolerant response compactors also enable efficient diagnosis essential to fast yield-learning.
5916562
Testing digital circuits with constraints
Many digital circuits have constraints on the logic values a set of signal lines can have. In this paper, we present two new techniques for detecting the illegal combinations of logic values in digital circuits and two techniques for preventing them from damaging the circuit or corrupting the test results. The hardware overhead of our technique is minimal and imposes negligible delay overhead. Simulation results show that the area overhead of our techniques is less than 1%. Unlike previous techniques, the fault coverage of the legal test patterns in a given test set is not sacrificed with our techniques. Furthermore, our techniques are applicable during IC production test, BIST, board-level tests and system-level tests.
35844193
Design for testability and testing of IEEE 1149.1 TAP controller
The Test Access Port (TAP) controller is a very important circuit present in all IC chips that are compliant with the IEEE 1149.1 Boundary Scan standard. Although the main purpose of boundary scan is to facilitate board-level testing, it is also used for many other testing and non-testing purposes (e.g., memory and logic BIST wrappers to enable embedded core test, programming FPGAs, checkpointing and recovery of dependable systems, etc.). Hence, it is important to thoroughly test the TAP controller before using it for other purposes. In this paper, we present techniques for designing and testing the TAP controller. Our design techniques simplify the procedure to test the TAP controller by orders of magnitude compared to previously published results. Our TAP controller design technique does not require any extra I/O pins and can be easily automated and incorporated into test tools.
2734062
A design diversity metric and reliability analysis for redundant systems
Design diversity has long been used to protect redundant systems against common-mode failures. The conventional notion of diversity relies on "independent" generation of "different" implementations. This concept is qualitative and does not provide a basis to compare the reliabilities of two diverse systems. In this paper, for the first time, we present a metric to quantify diversity among several designs. Based on this metric, we derive analytical reliability models that show a simple relationship between design diversity, system failure rate, and mission time. In addition, we present simulation results to demonstrate the effectiveness of design diversity in Duplex and Triple Modular Redundant (TMR) systems. For independent multiple-module failures, we show that, mere use of different implementations does not always guarantee higher reliability compared to redundant systems with identical implementations-it is important to analyze the reliability of redundant systems using our metric. For common-mode failures and design faults, there is a significant gain in using different implementations-however, as our analysis shows, the gain diminishes as the mission time increases. Our simulation results also demonstrate the usefulness of diversity for enhancing the self-testing properties of redundant systems.
11380579
Bitmap indexes for large scientific data sets: a case study
The data used by today's scientific applications are often very high in dimensionality and staggering in size. These characteristics necessitate the use of a good multidimensional indexing strategy to provide efficient access to the data. Researchers have previously proposed the use of bitmap indexes for high-dimension scientific data as a way of overcoming the drawbacks of traditional multidimensional indexes such as R-trees and KD-trees, which are bulky and whose performance does not scale well as the number of dimensions increases. However, the techniques proposed in previous work on bitmap indexes are not sufficient to address all problems that arise in practice. In experiments with real datasets, we experienced problems with index size and query performance. To overcome these shortcomings, we propose the use of adaptive, multilevel, multi-resolution bitmap indexes, and evaluate their performance in two scientific domains. Our preliminary experiments with a parallel query processor and index creator also show that it is very easy to parallelize a bitmap index
2578042
Trustworthy keyword search for regulatory-compliant records retention
Recent litigation and intense regulatory focus on secure retention of electronic records have spurred a rush to introduce Write-Once-Read-Many (WORM) storage devices for retaining business records such as electronic mail. However, simply storing records in WORM storage is insuffcient to ensure that the records are trustworthy, i.e., able to provide irrefutable proof and accurate details of past events. Specifically, some form of index is needed for timely access to the records, but unless the index is maintained securely, the records can in effect be hidden or altered, even if stored in WORM storage. In this paper, we systematically analyze the requirements for establishing a trustworthy inverted index to enable keyword-based search queries. We propose a novel scheme for effcient creation of such an index and demonstrate, through extensive simulations and experiments with an enterprise keyword search engine, that the scheme can achieve online update speeds while maintaining good query performance. In addition, we present a secure index structure for multi-keyword queries that supports insert, lookup and range queries in time logarithmic in the number of documents.
10906898
The Role of Statistical Models in Biometric Authentication
The current paper demonstrates the role of statistical models in authentication tasks – both in system development and in performance evaluation. We first introduce a model-based face authentication system based on the Fourier domain phase using Gaussian Mixture Models (GMM) which yields verification error rates as low as 0.3% on a face database of 65 individuals with extreme illumination variations. We then present a statistical framework for predicting authentication error rates for future populations in a rigorous way. This is in contrast to most evaluation protocols used today that are based on observational studies and valid only for the databases at hand. Applications establish that our model-based approach has better predictive performance than an existing state-of-the-art authentication technique.
62742629
Local facial asymmetry for expression classification
We explore a novel application of facial asymmetry: expression classification. Using 2D facial expression images, we show the effectiveness of automatically selected local facial asymmetry for expression recognition. Quantitative evaluations of expression classification using local asymmetry demonstrate statistically significant improvements over expression classification results on the same data set without explicit representation of facial asymmetry. A comparison of discriminative local facial asymmetry features for expression classification versus human identification is given.
35096806
Human Face Identification from Video Based on Frequency Domain Asymmetry Representation Using Hidden Markov Models
In this paper we introduce a novel human face identification scheme from video data based on a frequency domain representation of facial asymmetry. A Hidden Markov Model (HMM) is used to learn the temporal dynamics of the training video sequences of each subject and classification of the test video sequences is performed using the likelihood scores obtained from the HMMs. We apply this method to a video database containing 55 subjects showing extreme expression variations and demonstrate that the HMM-based method performs much better than identification based on the still images using an Individual PCA (IPCA) classifier, achieving more than 30% improvement.