Comparing shared and distributed memory computers

There are two distinct types of MIMD (Multiple Instruction, Multiple Data) computers: the shared memory machine, e.g. Butterfly, and the distributed memory machine, e.g. Hypercubes, Transputer arrays. Typically these utilize different programming models: the shared memory machine has monitors, semaphores and fetch-and-add; whereas the distributed memory machine uses message passing. Moreover there are two popular types of operating systems: a multi-tasking, asynchronous operating system and a crystalline, loosely synchronous operating system.

In this paper I firstly describe the Butterfly, Hypercube and Transputer array MIMD computers, and review monitors, semaphores, fetch-and-add and message passing; then I explain the two types of operating systems and give examples of how they are implemented on these MIMD computers. Next I discuss the advantages and disadvantages of shared memory machines with monitors, semaphores and fetch-and-add, compared to distributed memory machines using message passing, answering questions such as “is one model ‘easier’ to program than the other?” and “which is ‘more efficient‘?”. One may think that a shared memory machine with monitors, semaphores and fetch-and-add is simpler to program and runs faster than a distributed memory machine using message passing but we shall see that this is not necessarily the case. Finally I briefly discuss which type of operating system to use and on which type of computer. This of course depends on the algorithm one wishes to compute.     

Nucleus PLUS操作系统信号量机制的研究与测试

Nucleus PLUS是一种嵌入式实时操作系统内核.为深入全面地测试其用于任务同步的信号量模块,研究信号量实现机制,尤其是PI信号量中对优先级继承协议的实现,搭建测试环境,编写测试驱动,设计测试用例,开展针对信号量的测试.在常规测试、健壮性测试的基础上,提出基于信号量有限状态机的测试策略.测试效果良好,对操作系统其他内核对象的测试也具有一定的借鉴价值.     

一种基于VxWorks的高速实时数据记录系统的设计

本文针对大规模数据记录系统对嵌入式系统实现的实时性需求,设计了一种采用VxWorks操作系统的嵌入式实现方案,该方案采用模块化的设计架构,利用VxWorks灵活的多任务调度机制和任务间通信机制,建立了一种多任务间通信模型.通过对任务功能的合理划分和任务优先级的设置,该嵌入式系统克服了数据记录过程中数据丢失、数据覆盖的问题,提高了数据记录的实时性和可靠性要求.     

实时信号量机制的研究

随着实时嵌入式技术的发展,越来越多的实时系统采用Windows操作系统平台。为了满足实时系统严格的响应时间要求,增加Windows操作系统的实时能力非常必要。进程间的通信是任何一个实时操作系统中必不可少的一部分,在此分析Windows操作系统原有进程间通信的弊端,提出改进方法,在Windows操作系统上减少进程间通信所消耗的时间,提高进程间通信的效率。     

VxWorks操作系统下CompactPCI总线的驱动与控制技术

介绍了CompactPCI总线及接口技术,PCI配置空间的内容与操作方法.详细说明了在VxWorks实时多任务操作系统下配置cPCI总线设备的方法.由于系统通过中断响应外部事件,使得硬件中断处理成为实时系统设计中的关键问题.在VxWorks系统下对cPCI中断响应的主要操作是将外部中断与中断服务程序连接起来,并控制PCI9054接口芯片的中断控制寄存器.在中断服务程序中使用信号量实现任务间的同步,保证了系统实时数据采集的可靠性.     

Semi-open queuing networks: a review of stochastic models,solution methods and new research areas

Capturing the waiting times (at an external queue) for a customer to access a movable resource is an important step towards measuring customer service and system performance in manufacturing, logistics, communication and health care systems. Such waiting time measures are typically used for sizing resource and buffer capacities, and thereby minimising customer waiting time probabilities. In this regard, semi-open queuing networks (SOQNs), which decouple the arriving customers/transactions from the network resources using a synchronisation station (also known as a semaphore queue), can potentially capture the customer/transaction waiting times/costs more precisely and provide a rich network modelling construct. Hence, modelling manufacturing or service systems using SOQNs is an important step towards measuring customer flow times (sojourn times) wherein the customer waiting times at an external queue are a critical component. In this paper, we present several stochastic models for manufacturing and service systems using SOQNs and also discuss the potential applications of SOQNs. We then review the solution methods for SOQNs and also compare the numerical accuracies for three promising methods. Finally, we include the potential research areas in SOQNs.     

FPGA设计中信号量管理的硬件电路设计

在对嵌入式实时操作系统μC/OS-Ⅱ中任务之间通信进行深入研究的基础上,提出了将信号量的管理用基于FP-GA设计的硬件电路来完成,同时保证新的混合式实时操作系统对用户来说是透明的,即保证了混合式实时操作系统的可移植性.经过设计和不断地改进,混合式实时操作系统成功的移植到Altera公司的DE2-70开发板上,并完成了信号量管理的测试.这是一次探索性的设计,是混合式嵌入式实时操作系统设计中非常重要的一部分.     

一个多机系统中的硬件同步信号灯设计

一个多机系统中的硬件同步信号灯设计洪运麟，冯百明，肖骊在文献【ｌ」的基础上，进一步利用存储器芯片ＩＤＴ７０．２５的信号灯逻辑，开发了多机系统的硬件同步信号灯，大大简化了同步编程，可靠住和同步效率也有很大改进。每片ＩＤＴ７０２５带有八个信号灯逻辑［２」...     

并发进程同步算法的设计方法

论讨了并发进程的同步问题，给出一种以信号量为同步工具，借助前趋图进行同步算法设计的方法。