VLSI Based Interconnection Networks

Interest in tightly coupled multiprocessor computer systems has grown as the possibilities for high performance with such systems have been recognized. Central to their design is the structure of the network over which the processors communicate. Unless properly designed, such networks can be both a cost and performance bottleneck. This paper focuses on the design of VLSI communications networks, this is, on communications network which can be placed on a single VLSI chip. Traditional SSI-based boost and complexity measures for such networks have principally involved switch aggregate counts. In a VLSI domain, however, more appropriate measures involve chip area, and space-time product. The effects of network topology and VLSI layout on these measures are reviewed with regard to two network types. Another important question related to the VLSI communication network problem related to the chip pin constraints. This problem is discussed and some effects and options presented by bit slice network designs are described

PIN Limitations and VLSI Interconnection Networks

Multiple processor interconnection networks can be characterized as having N\u27 inputs and N\u27 outputs, each B\u27 bits wide. Construction of large networks requires partitioning of the N\u27*N\u27*B\u27 network into a collection of N*N switch modules of data size B (

Parallel Machines and Algorithms for Discrete-Event Simulations

A number of recent articles have focused on the design of high speed discrete-event simulation (DES) machines for digital logic simulation. These investigations are in response to the enormous costs associated with the simulation of complex (VLSI) digital circuits for logic verification and fault analysis. One approach to reducing simulation costs is to design special purpose digital computers that are tailored to the logic simulation test. This paper is concerned with the architecture of such logic machines. The paper has three principal parts. First, a taxonomy of logic machine architectures is presented. The taxonomy focuses on the central components of the logic simulation algorithms and on architectural alternatives for increasing the speed of the simulation process. It thus represents a basis for discussing and differentiating between proposed architectures and also results in the identification of several new architectures. Although developed for digital logic simulators., the taxonomy can be used for general DES machines. Second, a performance measure is presented which permits evaluation of DES machines. Finally several DES machine designs are described and categorized using the taxonomy

Regular Array Processors: Asynchronous Versus Clocked Control

Parallel computing structures consisting of large numbers of processors require synchronization so that data communication among processors is possible. Two basic methods of data synchronization, synchronous and asynchronous, are considered. The synchronous or clocked method uses a global clock for synchronization. Clock skew and clock line charge and discharge times both increase with system size. This decreases the data rates achievable and prevents the design of highly modular systems. The asynchronous method has no global control structure and results in a modular and expandable system with the data rate being independent of system size. It is however pin intensive. These two types of control schemes are modelled and the data rates achievable are determined and compared

Problems Encountered With Control Networks in Highly-Restructurable Digital Systems

This paper discusses problems encountered with control networks in highly restructurable digital systems. In particular the treatment of implementation errors is covered with emphasis on concurrent processing. The implementation of concurrent processing networks may result in errors which will be quite complex to detect and systematic methods are warranted. Four meta control elements are employed in obtaining convenient concurrent structures. We analyze several error detecting schemes and conclude that the arc-node method with node partitioning appears to be the most realistic approach at this time

Bypass versus Angioplasty in Severe Ischaemia of the Leg (BASIL) trial: Health-related quality of life outcomes, resource utilization, and cost-effectiveness analysis

BackgroundThe Bypass versus Angioplasty in Severe Ischaemia of the Leg (BASIL) trial showed that survival in patients with severe lower limb ischemia (rest pain, tissue loss) who survived postintervention for >2 years after initial randomization to bypass surgery (BSX) vs balloon angioplasty (BAP) was associated with an improvement in subsequent amputation-free and overall survival of about 6 and 7 months, respectively. We now compare the effect on hospital costs and health-related quality of life (HRQOL) of the BSX-first and BAP-first revascularization strategies using a within-trial cost-effectiveness analysis.MethodsWe measured HRQOL using the Vascular Quality of Life Questionnaire (VascuQol), the Short Form 36 (SF-36), and the EuroQol (EQ-5D) health outcome measure up to 3 years from randomization. Hospital use was measured and valued using United Kingdom National Health Service hospital costs over 3 years. Analysis was by intention-to-treat. Incremental cost-effectiveness ratios were estimated for cost per quality-adjusted life-year (QALY) gained. Uncertainty was assessed using nonparametric bootstrapping of incremental costs and incremental effects.ResultsNo significant differences in HRQOL emerged when the two treatment strategies were compared. During the first year from randomization, the mean cost of inpatient hospital treatment in patients allocated to BSX ($34,378) was estimated to be about$8469 (95% confidence interval, $2,417-$14,522) greater than that of patients allocated to BAP ($25,909). Owing to increased costs subsequently incurred by the BAP patients, this difference decreased at the end of follow-up to$5521 ($45,322 for BSX vs$39,801 for BAP) and was no longer significant. The incremental cost-effectiveness ratio of a BSX-first strategy was $184,492 per QALY gained. The probability that BSX was more cost-effective than BAP was relatively low given the similar distributions in HRQOL, survival, and hospital costs.ConclusionsAdopting a BSX-first strategy for patients with severe limb ischemia does result in a modest increase in hospital costs, with a small positive but insignificant gain in disease-specific and generic HRQOL. However, the real-world choice between BSX-first and BAP-first revascularization strategies for severe limb ischemia due to infrainguinal disease cannot depend on costs alone and will require a more comprehensive consideration of individual patient preferences conditioned by expectations of survival and other health outcomes

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

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