DDR2内存

在Inlel的计划表中，在2004年普及DDR2内存也是重要的一环，理论上说，DDR2在带宽提升，功耗，超频能力等方面比现有的DDR内存具有明显优势，采用DDR2带来性能提升简直是一定的……遗憾的是，这一幕也许不会很快变成事实，至少目前在i915/925平台上恐怕还难以得到体现。     

Embedded totally self-checking checkers: a practical design

In a totally self-checking (TSC) design, the circuit detects errors by monitoring redundantly coded data/control paths through a TSC checker. A problem arises when not all these code words are on the monitored lines during normal operation. A method of designing checkers that solves this difficulty is proposed. The method uses TSC checkers based on flip-flops instead of using the mostly combinational checkers now available. Two design applications are presented: TSC checkers for arithmetic AN codes, and a TSC iterative logic array     

Issues in using model checkers for test case generation

The use of model checkers for automated software testing has received some attention in the literature: It is convenient because it allows fully automated generation of test suites for many different test objectives. On the other hand, model checkers were not originally meant to be used this way but for formal verification, so using model checkers for testing is sometimes perceived as a “hack”. Indeed, several drawbacks result from the use of model checkers for test case generation. If model checkers were designed or adapted to take into account the needs that result from the application to software testing, this could lead to significant improvements with regard to test suite quality and performance. In this paper we identify the drawbacks of current model checkers when used for testing. We illustrate techniques to overcome these problems, and show how they could be integrated into the model checking process. In essence, the described techniques can be seen as a general road map to turn model checkers into general purpose testing tools.     

DDR:一种自适应的面向模式的软件体系结构

信息系统必须处于开放、可更改状态以响应对技术和需求的修改。为满足信息系统这种变化和演化的特征,提出了一种自适应的面向模式的软件体系结构,称之为“显示-定义-实现”(DDR)体系结构模式。描述了DDR体系结构模式适合的问题领域,并给出了相应的解决方案和组织结构。DDR体系结构模式由显示层、定义层与实现层组成。显示层是系统数据表现形式的实现,它实现了应用程序显示逻辑。定义层是DDR体系结构模式的核心,它封装了可更改的系统内部成分——通常以元对象的方式表示,所有元对象的集合形成定义层的数据字典。该层还提供了一个对外接口以方便对自身具体内容的修改,即元对象协议。实现层描述了开发应用功能的用户接口,实现了系统的业务逻辑。用DDR体系结构模式实现的系统,是一个自适应性系统,具有主动性、高安全性等特点,有利于系统的维护、扩展与移植。     

Structural redocumentation: a case study

Most software documentation typically describes the program at the algorithm and data-structure level. For large legacy systems, understanding the system's architecture is more important. The authors propose a method of reverse engineering through redocumentation that promises to extend the useful life of large systems     

Brick handling: a case study

A small change in brick dimensions resulted in an increase in the perceived work-load of men loading and unloading pallets of bricks by hand. A laboratory study indicated that the change in brick dimensions required changes in grip pattern in order to unload bricks at the same rate, moving the same number at a time. These changed grip patterns resulted in increased upper body movement, increased chest-muscle activity and higher heart rates. These differences were reflected in higher subjective ratings of fatigue.     

Robustness analysis: a case study

The stability test of polynomials whose coefficients depend multilinearly on interval parameters is considered. The authors describe and compare four brute-force solution approaches. These are eigenvalue calculation, zero exclusion from a specified value set, algebraic tests of real and complex Hurwitz roots, and the parameter space method. They are applied to a simple example with two parameters and third-order polynomial. An interesting feature of the example is that it can have an isolated unstable point. The example may be useful as a benchmark for future approaches to the multilinear problem. All four methods are shown to be feasible for the simple example, but they require effort     

DDR2存储系统动态匹配技术

随着同步动态随机存储器DDR2 SDRAM性能的日益提高,对存储系统的设计也提出了更高的要求.芯片内部动态电阻匹配技术是高性能DDR2存储系统设计中提高信号传输质量的关键技术.介绍了DDR2存储器中动态匹配技术的电路结构、信号反射分析以及匹配电阻的实现,指出了采用动态匹配技术的存储系统设计中需要着重考虑的关键问题,并通过软件模拟对动态匹配电路和传统的印制板匹配电路的信号进行了分析和对比.     

一种DDR SDRAM控制器的设计

在介绍DDR SDRAM控制器设计关键技术的基础上,讨论了一种DDR SDRAM控制器的设计方法.通过一种优化的地址映射策略提高了突发访问效率,采用0.18 μm CMOS工艺流片实现.所设计的DDR SDRAM控制器芯片在PCB板级测试中达到预期设计要求.     

Tank monitoring: a pAMN case study

The introduction of probabilistic behaviour into the B-method is a recent development. In addition to allowing probabilistic behaviour to be modelled, the relationship between expected values of the machine state can be expressed and verified. This paper explores the application of probabilistic B to a simple case study: tracking the volume of liquid held in a tank by measuring the flow of liquid into it. The flow can change as time progresses, and sensors are used to measure the flow with some degree of accuracy and reliability, modelled as non-deterministic and probabilistic behaviour respectively. At the specification level, the analysis is concerned with the expectation clause in the probabilistic B machine and its consistency with machine operations. At the refinement level, refinement and equivalence laws on probabilistic GSL are used to establish that a particular design of sensors delivers the required level of reliability.     

Incentives in production: a case study

The motivation, rationale, and experiences of implementing an incentive scheme in a large petrochemical plant in the People's Republic of China for the purpose of conserving the consumption of cooling water is described. Experimental implementation in a section of a plant is described in detail. A few incentive-induced features uncovered after analyzing the experimental data are reported. A mathematical model with several variations is presented. A better predictive property of the incentive scheme in comparison to a more conventional method is proved analytically. The effectiveness of the scheme is shown by the amount of water conserved, and by the management's decision for plantwide adoption of the scheme. Practical issues encountered in experimental implementation, extensions of the scheme to more general situations, and theoretical problem inspired by the experiment are discussed     

Measuring software quality: a case study

The National Security Agency's (NSA) mission is to provide support for the security of the United States. Over the years, the Agency has become extremely dependent on the software that makes up its information technology infrastructure. NSA has come to view software as a critical resource upon which much of the world's security, prosperity, and economic competitiveness increasingly rests. To ensure cost effective delivery of high quality software, NSA has analyzed effective quality measures applied to a sample code base of 25 million lines. This case study dramatically illustrates the benefits of code level measurement activities     

Value-based software engineering: a case study

The information technology field's accelerating rate of change makes feedback control essential for organizations to sense, evaluate, and adapt to changing value propositions in their competitive marketplace. Although traditional project feedback control mechanisms can manage the development efficiency of stable projects in well-established value situations, they do little to address the project's actual value, and can lead to wasteful misuse of an organization's scarce resources. The value-based approach to software development integrates value considerations into current and emerging software engineering principles and practices, while developing an overall framework in which these techniques compatibly reinforce each other.     

Job-shop development model: a case study

Traditional effort-estimation models can be frustrating, especially when staff are divided among multiple projects. The authors evaluate a model based on dividing activities into jobs. It accounts for divided time and more accurately categorizes rework costs. The model lets organizations represent software development in more detail than they can with many existing models. By breaking each project into batches and each batch into jobs, the model recognizes that, at any point in time, parts of the software may be at different stages of completion     

Learning without lectures: a case study

During a 1995-1996 sabbatical, the authors' long-standing concern about discrepancies between their teaching philosophies and classroom practices reached a crisis. As a result, they decided to offer the fall 1996 Introduction to Psychology course on the World Wide Web. There were several issues to think about. First, the authors saw the potential for a huge impact, since 80 to 85 percent of North Dakota State University students enrol in Psych110, most within their first two years. Second, they decided to design the course so that it could be offered for off-campus distance learning as well as on-campus resident instruction. Third, they decided to minimize overhead for students by using only a Web browser, e-mail, a textbook, and the textbook publisher's demonstration/simulation software. Fourth, they chose to base decisions about course components on published literature covering cognition and teaching. Finally, they built in mid term and final student course evaluation components and a field experiment comparing student attitudes and learning outcome for online versus lecture classes     

Intel's incident-free culture: a case study

The occupational ergonomic program that Intel's newly established manufacturing plant in Israel implemented in 1997 helped prevent injuries and also marked the launch of a whole new approach to ergonomics. A key element in the success of the seven-point program was a strong commitment from management, which came to regard this plan as a vital strategic element in the new plant's success. Comprehensive, top-down planning imposed obligations on all elements in the manufacturing spectrum, from suppliers to contractors to employees. Work requirements were set; cooperation with the plant's occupational health professionals was established; and long-term reporting and instruction systems were developed. Extensive ergonomic training was a crucial factor in integrating ergonomic procedures into the organization's day-to-day activities. Along with this instructional program, ergonomic engineers implemented a strict measuring system to ensure that each ergonomic activity would be performed according to schedule. By the time the factory opened its gates and began to produce, a vigorous ergonomic environment had emerged and employees were displaying an ergonomic mindset that also impinged upon their non-work activities. As a result of the successful implementation of the program, Intel's ergonomic program has become a model for Israeli industry. This paper presents a full ergonomic program that besides supplying the Intel plant with solutions was unique enough to impact the whole Israeli industry.     

Applying reliability measurement: a case study

The problem of knowing when to stop testing software is considered, focusing on the strategy of stopping when a reliability level or rate of failure occurrence acceptable to the customer is reached. The system's reliability is monitored throughout the system test, and the system is released to the field only when the measured reliability is at or above this objective. This approach was applied to test-failure data collected on Remote Measurement System-Digital 1, a large telecommunications testing system that had already gone through system test and been released to the field. The RMS-D1 failure data, which consisted of command-response errors versus commands executed, had been routinely collected by the system-test organization during testing. The testing phase analyzed, the load test, was an operational-profile-driven test in which a controlled load was imposed on the system reflective of the system's busy-hour usage pattern. It was found to be feasible to apply the reliability-measurement approach in real time, to systems actually undergoing system test, given a controlled load-test environment.<>     

Assessing architectural evolution: a case study

This paper proposes to use a historical perspective on generic laws, principles, and guidelines, like Lehman’s software evolution laws and Martin’s design principles, in order to achieve a multi-faceted process and structural assessment of a system’s architectural evolution. We present a simple structural model with associated historical metrics and visualizations that could form part of an architect’s dashboard. We perform such an assessment for the Eclipse SDK, as a case study of a large, complex, and long-lived system for which sustained effective architectural evolution is paramount. The twofold aim of checking generic principles on a well-know system is, on the one hand, to see whether there are certain lessons that could be learned for best practice of architectural evolution, and on the other hand to get more insights about the applicability of such principles. We find that while the Eclipse SDK does follow several of the laws and principles, there are some deviations, and we discuss areas of architectural improvement and limitations of the assessment approach.     

The Rochester checkers player: multimodel parallel programming foranimate vision

It is maintained that to exploit fully the parallelism inherent in animate vision systems, an integrated vision architecture must support multiple models of parallelism. To support this claim, the hardware base of a typical animate vision laboratory and the software requirements of applications are described. A brief overview is then given of the Psyche operating system, which was designed to support multimodel programming. A complex animate vision application, checkers, constructed as a multimodel program under Psyche, is also described. Checkers demonstrates the advantages of decomposing animate vision systems by function and independently selecting an appropriate parallel-programming model for each function     

基于FPGA的DDR2深存储设计

高存储深度是高端数字存储示波器的发展方向之一,应用DDR2存储器能够提高数字示波器的存储深度。本文中,设计并实现了采角IGbitDDR2的最大存储深度为256MB的深存储系统,作者介绍了利用MIG软件工具在Xilinx的Spartan一6系列FPGA中实现DDR2控制器的设计方法,详细叙述了其基本原理并给出了硬件测试结果。