Clock Distribution Methodology for PowerPC™ Microprocessors

Clock distribution design for high performance microprocessors has become increasingly challenging in recent years. Design goals of state-of-the-art integrated circuits, dictate the need for clock networks with smaller skew tolerances, large sizes, and lower capacitances. In this paper we discuss some of the issues in clock network design that arise in this context. We describe the clock design methodology and techniques used in the design of clock distribution networks for PowerPC? microprocessors that aim at alleviating some of these problems.

     

Clock Distribution Methodology for PowerPC? Microprocessors

Clock distribution design for high performance microprocessors has become increasingly challenging in recent years. Design goals of state-of-the-art integrated circuits, dictate the need for clock networks with smaller skew tolerances, large sizes, and lower capacitances. In this paper we discuss some of the issues in clock network design that arise in this context. We describe the clock design methodology and techniques used in the design of clock distribution networks for PowerPC microprocessors that aim at alleviating some of these problems.     

Relationships between anodic polarisation and corrosion of steel in concrete

Corrosion of reinforcement in concrete is a topic of concern mainly because of the high cost of repair and rehabilitation of concrete structural elements. There is as yet no method of assessment that would enable the rapid and accurate prediction of the extent of corrosion of reinforcing steel in concrete on site. Half cell potential techniques commonly used in situ give only probabilistic information on corrosion activity. Research effort is thus needed in both investigating and developing methods to assess more accurately the corrosion characteristics of steel in concrete with an ultimate view of site application. Long-term investigations on chloride induced corrosion of steel reinforcement have been conducted on a series of concrete slab specimens to establish relationships between electrochemical data and chloride induced corrosion of steel reinforcement. Potentiodynamic anodic polarisation procedures were used to monitor corrosion of steel reinforcement in concrete slab specimens over a period of four years. A statistically significant relationship between the area under the corrosion current and time relationship and the weight loss of steel reinforcement was established. Assessments of corrosion rates of steel in the concretes studied were thus verified. Reinforcement corrosion was found to be localised under the high chloride conditions occurring mainly in an area adjacent to the chloride source.     

Self-aligned on-chip coupled photonic devices using individual cadmium sulfide nanobelts

Nanowires (NWs) and nanobelts (NBs) have been widely studied and fabricated into a variety of nanoscale devices such as light emitting diodes (LEDs), lasers and biosensors. These unique materials have attracted sustained attention due to their novel properties, ease of growth, and the ability to fabricate highly engineered devices. However, their widespread application remains hindered due to the difficulty in integrating multiple NWs or NBs together for more complex devices. Integration of multiple NWs and NBs together on the same chip can enable the coupling of different devices to help realize complex on-chip architectures such as photonic integrated circuits or nanoscale diagnostic tools, which currently require outcoupling using larger components. In this letter we report the coupling of on-chip NB LEDs and photodetectors using a single, precisely self-aligned, cadmium sulfide (CdS) NB fabricated on a silicon-on-insulator (SOI) substrate. Electroluminescence generated by the CdS NB is waveguided and measured across the self-aligned device and demonstrates an on/off ratio of 102–103. This work describes a new method for fabricating and integrating more complex nanoscale devices that can enable advances in areas such as on-chip optical computational components and nanoscale optical biodiagnostics.