Microprocessor testability

As the level of microprocessor complexity increases to several hundred thousand transistors for a single-chip machine, it is becoming very difficult to test commercially available designs to the level of fault coverage desired by some customers. In order to achieve near 100-percent coverage of single stuck-at faults, future microprocessors must be designed with special testing features (designed for testability). The authors describe the testing problem for microprocessors, including the various methods of generating test sets and their application by the user. A survey of the testability features of some of today's commercially available microprocessors is presented. Suggestions for testability features for future-generation microprocessors are also discussed     

The effect of annealing on the microstructure and mechanical properties of Cu-X microcomposites

The effect of annealing on the microstructure, texture, and room-temperature mechanical properties ofin situ processed copper-based microcomposites has been investigated. These copper microcomposites, containing 15 vol pct Nb, Cr, or Ta, were produced by rolling of cast material. Annealing was carried out in vacuum for 10 hours at 250 °C, 400 °C, and 650 °C. Evidence of microstructural coarsening was found even at the lowest annealing temperature. The through-thickness microstructure of the composites was examined by transmission electron microscopy both before and after the annealing treatments. Texture of the as-processed micro-composites was assessed using X-ray diffraction methods. The strength of the composites following annealing was found to scale with the melting point of the second component. This article is based on a presentation made in the symposium “High Performance Copper-Base Materials” as part of the 1991 TMS Annual Meeting, February 17–21, 1991, New Orleans, LA, under the auspices of the TMS Structural Materials Committee.     

Identification of estrogen regulated genes in Fe33 rat hepatoma cells by differential display polymerase chain reaction and their hormonal regulation in rat liver and uterus

We applied the differential display RT-PCR (ddRT-PCR) technology to identify estrogen-regulated hepatic genes in the estrogen receptor expressing rat hepatoma cell line Fe33. Three genes of known sequences were detected by the ddRT-PCR approach: IGF binding protein-1 (IGFBP-1), vitamin D-dependent calcium-binding protein (CaBP9k) and major acute phase protein (MAP). Effects of ethinyl estradiol on the mRNA levels of these genes were confirmed by "Northern-blot" analysis. If given in combination with dexamethasone and glucagon, ethinyl estradiol caused 40-, 15- and 11-fold increases in the mRNA steady state level of IGFBP-1, CaBP9k and MAP, respectively, in Fe33 cells 24 h after addition of hormone. Besides ethinyl estradiol, the partial estrogen agonist OH-tamoxifen caused dose dependent effects on expression of MAP and IGFBP-1. Estrogen regulation of the respective genes and the modulatory effects of progesterone (10 mg/animal/day) were studied in ovariectomized rats treated subcutaneously for 14 days with 1 microgram/animal/day estradiol. "Northern-blot" analysis of liver RNA revealed a 6-fold stimulation of IGFBP-1 mRNA levels in estradiol-treated compared to vehicle-treated rats and a weak but detectable increase of MAP mRNA steady state level (1.6-fold) upon estradiol administration. No effect of estradiol treatment could be monitored for CaBP9k in rat liver. Modulatory effects of progesterone on estradiol-stimulated expression in the liver could be monitored for IGFBP-1 only. In an extension of our investigation on the expression of the three genes in rat liver, we determined their expression and hormonal regulation in the uterus of the same animals. In the uterus, estradiol caused an increase in CaBP9k mRNA. In contrast, IGFBP-1 mRNA levels increased dramatically upon progesterone administration, whereas no effect of estradiol treatment could be detected. MAP mRNA levels increased only after coadministration of estradiol and progesterone. In conclusion, the ddRT-PCR proved to be a powerful method to identify estrogen-regulated genes. The study on the hormonal regulation of three genes stimulated by estrogen in Fe33 cells revealed similarities and differences in their regulation in vivo and in vitro.     

Protein-structure-based prediction of animal model suitability for pharmacodynamic studies of subtype-selective estrogens

Subtype-selective estrogens are of increasing importance as tools used to unravel physiological roles of the estrogen receptors, ERalpha and ERbeta, in various species. Although human ERalpha and ERbeta differ by only two amino acids within the binding pockets, we and others recently succeeded in generating subtype-selective agonists. We have proposed that the selectivity of the steroidal compounds 16alpha-lactone-estradiol (16alpha-LE(2), hERalpha selective) and 8beta-vinyl-estradiol (8beta-VE(2), hERbeta selective) is based on the interaction of certain substituents of these compounds with essentially one amino acid in the respective ER binding pockets. For in vitro and ex vivo pharmacological experiments with these compounds we intended to use bovine tissues available from slaughterhouses in larger quantities. Using homology modeling techniques we determined that the amino acid conferring high hERbeta-selectivity to 8beta-VE(2) is not exchanged between human and bovine ERalpha and bovine ERbeta. Thus, we predicted our steroidal hERbeta-selective compound to exhibit only weak agonistic activity at bERbeta and that bovine tissue is therefore not suited for investigation of ERbeta functions. The situation is presumably identical for pig, sheep, and the common marmoset, whereas rats, mice, and rhesus macaques are appropriate animal models to study pharmacological effects of 8beta-VE(2) in vivo. This prediction was confirmed in transactivation studies assessing estradiol (E(2)) and the two subtype-selective ligands on bovine ERbeta and on a series of hERalpha and hERbeta with mutations in their respective ligand-binding pockets. We have shown that the detailed understanding of the interactions of a compound with its target protein enables the identification of relevant species for pharmacological studies.     

S-N Curve inversion of a nickel-base superalloy at elevated temperature

Stress controlled tensile fatigue behavior of a representative nickel-base superalloy, Udimet 115, was studied at 760 °C and at 1 Hz while holding the maximum stress constant. An inversion in the S-N curve was observed within 10₄ cycles, in contrast to normal S-N behavior at ambient temperatures. A detailed analysis of the strain response to a trapezoidal applied stress waveform indicated that the inversion is consistent with increasing creep strains due to increasing mean stresses. Fractographic observations were also found to be consistent with the inversion in that, at higher mean stresses, intergranular fracture replaced the usual stage II-type intragranular fracture associated with fatigue failure in these planar-slip alloys. The results are also discussed with respect to the three regimes of dynamic creep and the observed plastic increments and anelastic strains.     

Design for testability and built-in self test: a review

A summary is presented of a number of design-for-testability (DFT) and built-in self-test (BIST) schemes that can be used in modern VLSI circuits. The DFT methods presented are used to increase the controllability and observability of the circuit design. Partitioning, bus architectures, test-point insertion, and scan methods are discussed. On-chip hardware for real-time test-pattern generation and data compression are investigated. Several of the DFT methods are then combined to form BIST hardware configurations. Built-in evaluation and self-test (BEST), autonomous test, scan with random inputs, built-in logic block observer (BILBO), partitioning with BEST, test-point insertion with on-chip control, and combined test-pattern generation and data compression (CTGC) are considered. An overview of each BIST scheme is offered     

Induced creep and creep/fatigue of a nickel-base superalloy at ambient temperatures

The stress controlled fatigue of Nimonic*115, a typical γ’-strengthened nickel-base superalloy, was studied at ambient temperature, using a trapezoidal wave form at 1 Hz, with stresses chosen to produce failure in the lO⁴ to lO⁴ cycle range. In tests with maximum stress greater than the proportional limit, most of the fatigue damage occurs within the first few test cycles. Much of this strain is accumulated under static load and is therefore identified as creep strain. Transmission electron microscopy shows that these creep strains occur in slip bands which disrupt the ordered γ’ precipitates. Strain is found to follow a logarithmic time dependence, which suggests a low activation energy mechanism.     

Quiescent power supply current measurement for CMOS IC defectdetection

Quiescent power supply current (I_DDQ) measurement is a very effective technique for detecting in CMOS integrated circuits (ICs). This technique uniquely detects certain CMOS IC defects such as gate oxide shorts, defective p-n junctions, and parasitic transistor leakage. In addition, I_DDQ monitoring will detect all stuck-at faults with the advantage of using a node toggling test set that has fewer test vectors than a stuck-at test set. Individual CMOS ICs from three different fabrication sites had a unique pattern or fingerprint of elevated I_DDQ states for a given test set. When I_DDQ testing was added to conventional functional test sets, the percentage increase in failures ranged from 60% to 182% for a sample of microprocessor, RAM, and ROM CMOS ICs