A product information modeling framework for product
lifecycle management
R.Sudarsan *,S.J.Fenves,R.D.Sriram,F.Wang
Manufacturing Systems Integration Division,Manufacturing Engineering Laboratory,National Institute of Standards and Technology,
Gaithersburg,MD 20899,USA
Accepted 2February 2005
Abstract
The Product Lifecycle Management (PLM)concept holds the promise of seamlessly integrating all the information produced throughout all phases of a product’s life cycle to everyone in an organization at every managerial and technical level,along with key suppliers and customers.PLM systems are tools that implement the PLM concept.As such,they need the capability to serve up the information referred to above,and they need to ensure the cohesion and traceability of product data.
We describe a product information-modeling framework that we believe can support the full range of PLM information needs.The framework is based on the NIST Core Product Model (CPM)and its extensions,the Open Assembly Model (OAM),the Design-Analysis Integration model (DAIM)and the Product Family Evolution Model (PFEM).These are abstract models with general semantics,with the speci?c semantics about a particular domain to be embedded within the usage of the models for that domain.CPM represents the product’s function,form and behavior,its physical and functional decompositions,and the relationships among these concepts.An extension of CPM provides a way to associate design rationale with the product.OAM de?nes a system level conceptual model and the associated hierarchical assembly relationships.DAIM de?nes a Master Model of the product and a series of abstractions called Functional Models—one for each domain-speci?c aspect of the product—and two transformations,called idealization and mapping,between the master model and each functional model.PFEM extends the representation to families of products and their components;it also extends design rationale to the capture of the rationale for the evolution of the families.
The framework is intended to:(1)capture product,design rationale,assembly,and tolerance information from the earliest conceptual design stage—where designers deal with the function and performance of products—to the full lifecycle;(2)facilitate the semantic interoperability of next-generation CAD/CAE/CAM systems;and (3)capture the evolution of products and product families.The relevance of our framework to PLM systems is that any data component in the framework can be accessed directly by a PLM system,providing ?ne-grained access to the product’s description and design rationale.q 2005Elsevier Ltd.All rights reserved.
Keywords:Product Lifecycle Management (PLM);Core Product Model;Open Assembly Model;Interoperability;Ontology;Standards
1.Introduction
PLM is generally de?ned as ‘a strategic business approach for the effective management and use of corporate intellec-tual capital’[1].PLM systems are gaining acceptance for
managing all information about a corporation’s products throughout the products’full lifecycle.Global competition is one of the key drivers for many organizations to adopt the PLM concept and implement PLM systems.The PLM concept aims to streamline product development and boost innovation in manufacturing.Hence the PLM concept is a strategic business approach for the effective creation,management and use of corporate intellectual capital,from a product’s initial conception to its retirement [1].
Even in the current (2003)economic downturn,many manufacturing companies are investing in PLM systems—to the tune of $2.3billion this year [2].We believe the reason why these companies are willing to take the risk is that these companies see PLM’s potential to vastly
improve
Computer-Aided Design 37(2005)1399–1411
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0010-4485//$-see front matter q 2005Elsevier Ltd.All rights reserved.doi:10.1016/j.cad.2005.02.010
*Corresponding author.Address:George Washington University,Washington,DC 20052,USA.Tel.:C 130********;fax:C 130********.
E-mail addresses:sudarsan@https://www.doczj.com/doc/3817869812.html, (R.Sudarsan),sfenves@https://www.doczj.com/doc/3817869812.html, (S.J.Fenves),sriram@https://www.doczj.com/doc/3817869812.html, (R.D.Sriram),fuwang@https://www.doczj.com/doc/3817869812.html, (F.Wang).
their ability to innovate,get products to market faster, and reduce errors.According to industry analyst CIMdata,“For an enterprise to be successful in today’s and tomorrow’s global markets,PLM is not an option—it is a competitive necessity”[1].
A critical aspect of PLM systems is their product information modeling architecture.Here,the traditional hierarchical approach to building software tools presents a serious potential pitfall:if PLM systems continue to access product information via Product Data Management(PDM) systems which,in turn,obtain geometric descriptions from Computer-Aided Design(CAD)systems,the information that becomes available will only be that which is supported by these latter systems.
In this paper,a different approach to serving up information to PLM systems is proposed:a single PLM system support framework for product information that can access,store,serve,and reuse all the product information throughout the entire product lifecycle.This framework and its components are presented after a brief discussion of the PLM concept and of the major PLM system architecture and interoperability issues.
1.1.The PLM concept
PLM holds the promise of seamlessly integrating and making available all of the information produced through-out all phases of a product’s life cycle to everyone in an organization,along with key suppliers and customers. Manufacturers can shrink the time it takes to introduce new product models in a number of ways.Product engineers can dramatically shorten the cycle of implementing and approving engineering changes across an extended design chain.Purchasing agents can work more effectively with suppliers to reuse parts.Executives can take a high-level view of all important product information,from details of the manufacturing line to parts failure rates culled from warranty data and information collected in the?eld.
Because PLM systems grew out of product design software,company management tends to delegate the PLM concept to engineering executives,who traditionally have managed their own technology rollouts.While this hands-off approach works for choosing point solutions,such as CAD tools,it does not work well for a company-wide integrated platform.Different business functions generate and deal with product data in disparate ways.Manufacturing and engineering,for instance,work with a different version of a bill of materials—a listing of parts and subassemblies making up a product—than does purchasing,which also relies on approved vendor lists and catalogs.
For the PLM concept to be successful,issues such as establishing data standards and designing corporation-wide integration architectures need to be addressed so that formerly fragmented information can be served up to individuals in a format they can use.That way,people in various divisions are equipped to make key decisions—such as what products to introduce or what features to include in a product’s design phase—when they are most cost-effective, rather than midstream in the parts procurement stage or even during manufacturing.
1.2.PLM system architecture and interoperability issues
PLM systems are tools that assist a corporation in the implementation of PLM concepts.One of the main questions regarding PLM systems is:“What constitutes the PLM systems’functionality?”The full PLM system functionality can be achieved by the speci?c components illustrated in Fig.
1.These are:(1)an Information Technology(IT)Infrastruc-ture;(2)a Product Information Modeling Architecture;(3)a Development Toolkit and Environment;and(4)a set of Business Applications.The IT infrastructure is the foun-dation that includes hardware,software,and Internet technologies,underlying representation and computing languages,and distributed objects and components.
The product information modeling architecture includes product ontology and interoperability standards.The development toolkit and environment provide the means for building Business Applications that provide the initial functionality and enhance and extend the functionality of the PLM concept and could include kernels(e.g.geometry, math),visualization tools,data exchange standards and mechanisms,and databases.The business applications provide the PLM functionality that processes the corporate intellectual capital.
In two recent NIST workshops held in2003,attempts were made to describe an architecture for the lifecycle-wide management and integration of product data[4,5].The architecture,as described in the working draft of the workshops’summary report,is intended to provide a roadmap for the application of the diverse information technologies and computer science concepts that may be used to build and operate PLM systems supporting the full product lifecycle[6].
The domain of application for the resulting PLM system considered in the workshops deals with
complex Fig.1.A conceptual PLM system architecture.
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engineered-to-order systems,such as found in the aerospace and defense industries.The architecture de?nes two classes of views of product data:semantic views de?ne constraints on the interpretation and usage of the information;while infrastructural views relate to the encoding and composition of data in the processes and tools in which it is used. Potentially applicable technologies are discussed in the working draft with respect to these two classes of views.
Some of the principal concerns expressed in the NIST planning meetings were the cohesion and traceability of product data.The conclusion was that current data management practices do not provide suf?cient support of data cohesion and traceability.Cohesion and trace-ability,however,are complex and abstract goals when viewed as attributes of an information https://www.doczj.com/doc/3817869812.html,rmation technology does not address these goals directly;rather, certain other qualities help to support these goals.Among the major constituent properties of cohesion and trace-ability identi?ed were associativity across viewpoints and logical consistency[6].
PLM systems form the apex of the corporate software hierarchy and frequently implemented so that they depend on subsidiary systems for detailed information capture and dissemination.PLM systems therefore tend to delegate the task of managing the information describing the product itself to Product Data Management(PDM)systems. Furthermore,in many organizations,only the geometric description of products generated by Computer-Aided Design(CAD)systems is managed directly;in these organizations PDM systems rely on the CAD systems for managing product descriptions.
The above segmentation of PLM and subsidiary software systems results in three shortcomings.First,while PLM systems can track changes through the products’lifecycle from conception to disposal,the information that describes the actual changes can be found only through the subsidiary PDM systems,and the reason for the changes may not be recorded in computer-processable form anywhere.Thus, there is a need to make product descriptions and their design rationale directly accessible from PLM systems,with no intermediary layers of software.Second,CAD represen-tations of form(geometry)arise only at later stages of design, after a geometry has been assigned to the product concept; therefore,PLM systems tied only to CAD representations of products cannot be useful before the form is assigned.In order to realize the PLM concept’s full potential,PLM systems need to interact with product information used in the early stages of conception and ideation,where designers and planners deal with the function and performance of products, and not yet with their form.Third,at the opposite end of the product’s lifecycle,during manufacturing,installation, operation,maintenance and,eventually,disposal,the form of the product changes little,while much information is gathered about the product’s behavior in these lifecycle stages.Here again,PLM systems tied only to CAD representations of products cannot be useful;PLM systems need to interact with product behavior information in the late stages of the lifecycle.
PLM systems are still in the very early stages and are in a ?ux.This may lead to the development of many proprietary systems and interfaces,which would result in additional interoperability problems.Hence we need national and international efforts to develop standards to alleviate future interoperability problems for PLM systems.We have made it our goal in the Product Engineering Program at the National Institute of Standards and Technology in the US to establish a semantically based,validated product represen-tation scheme as a standard that supports the seamless interoperability among current and next generation compu-ter-aided design(CAD)systems and between CAD systems and other systems that generate and use product.As part of this effort,we are developing a framework and a representation scheme that will address some of the above-mentioned issues.
The focus of this paper is the second component of the PLM system architecture presented in Fig.1,namely,the product information modeling architecture.The aim of the paper is to argue that the Product Engineering Program’s approach can:(1)support the full range of PLM information needs;and(2)overcome the three shortcomings of the PLM software segmentation discussed above.The paper is organized as follows.In Section2we introduce the NIST information-modeling framework.In Section3,we describe the four components of the NIST information modeling framework.Further research issues to be addressed are discussed in Section4.Finally the conclusions are given in Section5.
2.The NIST information modeling framework
The exchange of product,part and assembly information between heterogeneous modeling systems is critical for collaborative design and manufacturing.Interchange stan-dards for product geometry are in wide use.However,little has been done in terms of developing standard represen-tations that specify the full range of design information and product knowledge.The NIST information-modeling fra-mework is intended to address this issue.
The conceptual product information modeling frame-work under development at NIST has the following key attributes:(1)it is based on formal semantics,and will eventually be supported by an appropriate ontology to permit automated reasoning;(2)it is generic:it deals with conceptual entities such as artifacts and features,and not speci?c artifacts such as motors,pumps or gears;(3)it is to serve as a repository of a rich variety of information about products,including aspects of product description that are not currently incorporated;(4)it is intended to foster the development of novel applications and processes that were not feasible in less information-rich environments;(5) it incorporates the explicit representation of design
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rationale,considered to be as important as that of the product description itself;and (6)there are provisions for converting and/or interfacing the generic representation schemes with a production-level interoperability frame-work.An implementation of the information modeling framework will:(1)provide a generic repository of all product information at all stages of the design process;(2)serve all product description information to the PLM system and its subsidiary systems using a single,uniform information exchange protocol;and (3)support direct interoperability among CAD,CAE,CAM and other interrelated systems where high bandwidth,seamless information interchange is needed.
To better understand the high-level view of PLM framework we adapted the epicycle diagram from [7]to describe the process and information ?ows in any product lifecycle 1.The Figs.2and 3explains the epicycle nature of PLM.The Fig.2characterizes the information ?ow pattern in the PLM,as it perceived today.In Fig.3the mediation of information ?ow across the activities of PLM are done through a common set of ontological structure,and information models to represent product and process.The concept of product information model framework is derived from the traditional engineering design,functional reasoning,and product modeling [8–11].The main focus of
this paper is to synthesize these representations in the context of engineering information exchange as well as in the context of computational models.
https://www.doczj.com/doc/3817869812.html,ponents of the information modeling framework The NIST information-modeling framework consists of the four major components as sown in Fig.
4.The dependency relationships (represented by dashed arrows)among these packages show that there exist certain association or generalization relationships among classes in the different packages.In this paper,we only give brief descriptions of these packages.The models are explained in more detail elsewhere,using an example [12–14].3.1.The core product model
The primary objective of the Core Product Model (CPM)is to provide a base-level product model that is open,non-proprietary,generic,extensible,independent of any one product development process and capable of capturing the full engineering context commonly shared in product development [15].Throughout the paper we use the notation and class diagrams of the Uni?ed Modeling Language (UML)[16],we also use bold face font for UML
classes
Fig.2.PLM epicycle-current view.
1
We thank E.Subrahmanian (Carnegie Mellon)in developing this ?gure.
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and packages,where a package in UML is a collection of classes that can be used as a namespace.
Fig.5illustrates the entities comprising the CPM.All entities are specializations of the abstract class Common-CoreObject .CoreEntity and CoreProperty are abstract classes.The former specializes into Artifact and Feature ,and the latter into Function ,Form ,Geometry ,and Material .A DesignRationale class (discussed in Section 3.4)is associated with CoreProperty .
Artifact is the aggregation of Function ,Form ,and Behavior .Form in turn is the aggregation of Geometry and Material .In addition,an Artifact has a Speci?cation and is an aggregation of Features .Feature represents any information in the Artifact that is an aggregation of Function and Form .Artifact ,Feature ,Function ,Form ,Geometry and Material are each aggregates of their own containment hierarchies (part-of relationships).
Semantically,Artifact represents a distinct entity in a product,whether that entity is the entire product or one of its subsystems,parts or components.Function represents what the artifact is intended to do.The distinct representation of Function renders the core product model and its extensions capable of supporting functional reasoning in the absence of any information on the artifact’s form,thus providing support for the conceptual phases of design.
Form may be viewed as the proposed design solution to the problem speci?ed by the function and consists of the artifact’s Geometry (shape and structure may be
synonymous to geometry in some contexts)and the Material it is composed of.Behavior represents how the artifact’s form implements its function;one or more causal models,such as Finite Element Analysis (FEA)or Computational Fluid Mechanics (CFM)models,may be used to evaluate it.Cost,manufacturability,durability,etc.are examples of other behavioral models that may be incorporated.As stated above concerning function,this extended representation of behavior renders the core product model and its extensions capable of supporting behavioral reasoning at all stages of the product’s lifecycle.Feature represents a subset of the form that has some function assigned to it.CPM does not treat pure form elements as features,nor does it support the independent behavior of features.
Fig.6shows the relationships in the CPM.All relation-ships are subclasses of the abstract class CommonCore-Relationship and are all UML association
classes.
Fig.3.PLM epicycle-mediated
view.
Fig.4.Framework components.
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Requirement is an association class between the Speci?ca-tion and a CoreProperty of the artifact;each requirement applies to some aspect of the function,form,geometry or material of the artifact (purists in design theory may argue that requirements may only address function,but in practice many aspects of form may be speci?ed without giving a speci?c functional justi?cation).Constraint links a set of CoreProp-erty entities that share an attribute that must hold in all cases.There are two specializations of SetRelationship :UndirectedSetRelationship groups objects into a set,while DirectedSetRelationship groups them into two subsets with different roles (e.g.a controlling subset and a controlled-by subset).AssemblyRelationship is implemented in the CPM as an undirected set of artifacts and features;it is specialized in the Open Assembly Model described below.Finally,a Reference links or cross-references entities.
3.2.The open assembly model
Most electromechanical products are assemblies of components.The aim of the Open Assembly Model (OAM)is to provide a standard representation and exchange protocol for assembly and system-level tolerance infor-mation.OAM is extensible;it currently provides for tolerance representation and propagation,representation of kinematics,and engineering analysis at the system level [17].The assembly information model emphasizes the nature and information requirements for part features and assembly relationships.The model includes both assembly as a concept and assembly as a data structure.For the latter it uses the model data structures of ISO 10303,informally known as the Standard for the Exchange of Product model data (STEP)[3,18].Fig.7shows the main schema of the Open Assembly Model.The schema incorporates infor-mation about assembly relationships and component composition;the former is represented by the class AssemblyAssociation and the latter is modeled using part-of relationships.The class AssemblyAssociation represents the component assembly relationship of an assembly.It is the aggregation of one or more Artifact Association s.
An ArtifactAssociation class represents the assembly relationship between one or more artifacts.For most
cases,
Fig.5.Entities in the core product
model.
Fig.6.Relationships in the core product model.
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the relationship involves two or more artifacts.In some cases,however,it may involve only one artifact to represent a special situation.Such a case may occur when an artifact is to be ?xed in space for anchoring the entire assembly with respect to the ground.It can also occur when kinematic information between an artifact at an input point and the ground is to be captured.Such cases can be regarded as relationships between the ground and an artifact.Hence,we allow the artifact association with one artifact associated in these special cases.
An Assembly is decomposed into subassemblies and parts.A Part is the lowest level component.Each assembly component (whether a sub-assembly or part)is made up of one or more features,represented in the model by OAMFeature .The Assembly and Part classes are subclasses of the CPM Artifact class and OAMFeature is a subclass of the CPM Feature class.ArtifactAssociation is specialized into the following classes:PositionOrienta-tion ,RelativeMotion and Connection .PositionOrienta-tion represents the relative position and orientation between two or more artifacts that are not physically connected and describes the constraints on the relative position and orientation between them.RelativeMotion represents the relative motions between two or more artifacts that are not physically connected and describes the constraints on the relative motions between them.Connection represents the connection between artifacts that are physically connected.Connection is further specialized as FixedConnection ,MovableConnection ,or IntermittentConnection .Fixed-Connection represents a connection in which the participat-ing artifacts are physically connected and describes the type and/or properties of the ?xed joints.MovableConnection represents the connection in which the participating artifacts are physically connected and movable with respect to one another and describes the type and/or properties of kinematic joints.IntermittentConnection represents the connection in which the participating artifacts are physically connected only intermittently.
OAMFeature has tolerance information,represented by the class Tolerance ,and subclasses AssemblyFeature and CompositeFeature .CompositeFeature represents a com-posite feature that can be decomposed into multiple simple features.AssemblyFeature ,a sub-class of OAMFeature ,is de?ned to represent assembly features.Assembly features are a collection of geometric entities of artifacts.They may be partial shape elements of any artifact.For example,consider a shaft-bearing connection.A bearing’s hole and a shaft’s cylinder can be viewed as the assembly features that describe the physical connection between the bearing and the shaft.We can also think of geometric elements such as planes,screws and nuts,spheres,cones,and toruses as assembly features.The class AssemblyFea-tureAssociation represents the association between mating assembly features through which relevant artifacts are associated.
The class ArtifactAssociation is the aggregation of AssemblyFeatureAssociation .Since associated artifacts can have multiple feature-level associations when assembled,one artifact association may have several assembly features associations at the same time.That is,an artifact association is the aggregation of assembly feature associations.Any assembly feature association relates in general to two or more assembly features.However,as in the special case where an artifact association involves only one artifact,it may involve only one assembly feature when the relevant artifact association has only one artifact.The class AssemblyFeatureAssociationRepresentation rep-resents the assembly relationship between two or
more
Fig.7.Main schema of open assembly model.
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assembly features.This class is an aggregation of parametric assembly constraints,a kinematic pair,and/or a relative motion between assembly features.Parametri-cAssemblyConstraint speci?es explicit geometric con-straints between artifacts of an assembled product,intended to control the position and orientation of artifacts in an assembly.Parametric assembly constraints are de?ned in ISO 10303-108[19]).This class is further specialized into speci?c types:Parallel ,ParallelWithDimension ,SurfaceDistanceWithDimension ,AngleWithDimension ,Perpendicular ,Incidence ,Coaxial ,Tangent ,and FixedComponent .
KinematicPair de?nes the kinematic constraints between two adjacent artifacts (links)at a joint.The kinematic structure schema in ISO 10303-105[20]de?nes the kinematic structure of a mechanical product in terms of links,pairs,and joints.The kinematic pair represents the geometric aspects of the kinematic constraints of motion between two assembled components.KinematicPath represents the relative motion between artifacts.The kinematic motion schema in ISO 10303-105[20]de?nes kinematic motion.It is also used to represent the relative motion between artifacts.
Tolerancing is a critical issue in the design of electro-mechanical assemblies.Tolerancing includes both tolerance analysis and tolerance synthesis.In the context of electro-mechanical assembly design,tolerance analysis refers to evaluating the effect of variations of individual part or subassembly dimensions on designated dimensions or functions of the resulting assembly.Tolerance synthesis refers to allocation of tolerances to individual parts or sub-assemblies based on tolerance or functional requirements on the assembly.Tolerance design is the process of deriving a description of geometric tolerance speci?cations for a product from a given set of desired properties of the product.Existing approaches to tolerance analysis and synthesis entail detailed knowledge of the geometry of the assemblies and are mostly applicable only during advanced stages of design,leading to a less than optimal design.During the design of an assembly,both the assembly structure and the associated tolerance information evolve continuously;signi?cant gains can thus be achieved by effectively using this information to in?uence the design of that assembly.Any proactive approach to assembly or tolerance analysis in the early design stages will involve making decisions with incomplete information models.In order to carry out early tolerance synthesis and analysis in the conceptual product design stage,we include function,tolerance,and behavior information in the assembly model;this will allow analysis and synthesis of tolerances even with the incomplete data set.In order to achieve this we de?ne a class structure for tolerance speci?cation and we describe this in Fig.8.
DimensionalTolerance typically controls the variability of linear dimensions that describe location,size,and angle;it is also known as tolerancing of perfect form.This is included to accommodate the ISO 1101standard [21].GeometricTolerance is the general term applied to the category of tolerances used to control shape,position,and runout.It enables tolerances to be placed on attributes of features,where a feature is one or more pieces of a part surface;feature attributes include size (for certain features),position (certain features),form (?atness,cylin-dricity,etc.),and relationship (e.g.perpendicular-to).The class GeometricTolerance is further specialized into the following:(1)FormTolerance ;(2)Pro?leTolerance ;(3)RunoutTolerance ;(4)OrientationTolerance ;and (5)LocationTolerance .
Datum is a theoretically exact or a simulated piece of geometry,such as a point,line,or plane,from which a tolerance is referenced.DatumFeature is a physical feature that is applied to establish a datum.FeatureOfSize is a feature that is associated with a size dimension,such as the diameter of a spherical or cylindrical surface or the distance between two parallel planes.StatisticalControl is a speci?cation that incorporates statistical process controls on the toleranced feature in
manufacturing.
Fig.8.Tolerance model.
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3.3.The design-analysis integration model
Computer-Aided Design,for generating a product’s geometry,and Computer-Aided Engineering,for analyses of its behavior,are both in common use today.Typically,a product’s behavior needs to be analyzed in several functional domains(e.g.structural,thermal,kinetics, economics)and the results of the analyses may suggest design changes for improving or optimizing the behavior. However,the integration of the efforts of the professionals in the two disciplines of spatial and functional design is not as complete as it should be,resulting in the limited interoperability of the two sets of tools.
The Design-Analysis Integration Model(DAIM)is a conceptual data architecture that provides the technical basis for tighter design-analysis integration than is possible with today’s tools and information models.It is also intended to make analysis-driven design(often referred to as form-to-function reasoning)more practical.Eventually,it should also support opportunistic analysis,where the system tracks the geometric design process and noti?es the designer when suf?cient geometric information has been generated to initiate a functional analysis[22].
The class diagram of the DAIM is shown in Fig.9. MasterModel and FunctionalModel are both specializ-ations of the CPM Artifact class;the latter also serves as the organizing principle for all information in the DAIM.The Master Model serves as the global repository of information on a product;in practice,it may be implemented as a centralized,distributed,federated or virtual database.Each FunctionalModel represents an abstraction of the product of interest to a speci?c functional domain at a particular stage in the lifecycle of a product.The?gure shows three representative specializations:a StrengthView for?nite element modeling and analysis;a ShapeView for classical CAD geometry modeling;and a KinematicsView for kinematic modeling and analysis.
Two association classes link the master and functional models.Idealization provides the transformation that creates a functional model speci?c to a particular domain from the master model;this is typically an abstraction operation removing detail irrelevant to the particular function,but more general transformations may also be used.Mapping provides the reverse transformation of updating the master model based on changes in the domain-speci?c functional model;it is conceptually the more dif?cult transformation to de?ne and develop for the various functional domains of interest,as it is responsible for maintaining full logical consistency between the two models.
3.4.The product family evolution model
Many manufacturing concerns develop product families so as to offer a variety of products with reduced development costs[23].The Product Family Evolution Model(PFEM)represent the evolution of product families and of the rationale of the changes involved[24].The model consists of three sub-models:family,evolution,and evolution rationale.
A product is made up of components that usually have their own family de?nitions.Therefore,product and component families are modeled separately,and con?gur-ation relationships established between products and their components.The class PFEM_Artifact,a specialization of the CPM Artifact class,represents the design information about an artifact in the family.
Fig.10shows the class diagram.Family,Series,and Version are subclasses of FamilyDesignation.Family is the designation for an entire artifact family,a collection of Series that may have sub-series.Series,in turn,are composed of a chronologically sequenced chain structure of Version s.
ProductFamily and ComponentFamily,ProductSeries and ComponentSeries,and ProductVersion and Compo-nentVersion are subclasses of Family,Series,and Version, respectively.Con?guration is the association class between ProductVersion and ComponentVersion that de?nes the actual con?guration of component versions in each of the product versions.Family Evolution.Family
Evolution Fig.9.Design-analysis integration model.
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consists of two aspects:Family Derivation and Design Evolution.Family Derivation contains the precedence relationships between series and versions in the evolution of the product line.Design Evolution contains the design information characterizing the changes between particular series or versions and their predecessor(s).
Fig.11shows the class diagram of family evolution.The class Evolution is the aggregation of FamilyDerivation and DesignEvolution .FamilyDerivation is specialized into SeriesDerivation and VersionDerivation .SeriesDer-ivation is the association class between a series and its predecessor series,and VersionDerivation is the associ-ation class between a version and its predecessor version(s).DesignEvolution is the association class between a PFEM_Artifact of a series or version and that of its predecessor series or version.
Evolution Rationale .While Family Evolution captures what has changed,Evolution Rationale captures the reasons for the changes.The evolution rationale includes two aspects:FamilyDerivationRationale and DesignEvolu-tionRationale .Family Derivation Rationale captures the driving factors for the changes in the product line while
Design Evolution Rationale records the reasons for the design changes.
The class EvolutionRationale is de?ned in the package Rationale ,shown in Fig.12.The classes DesignRationale and EvolutionRationale are subclasses of Rationale .The class DesignJusti?cation de?nes the justi?cation of the design decision to use the associated artifact,and is the principal contents of the design rationale.
A representative set of specializations of DesignJusti?ca-tion is shown in the ?gure.DesignEvolutionRationale and FamilyDerivationRationale are subclasses of EvolutionRa-tionale.DevelopmentSpeci?cationEvolution represents the evolution of DevelopmentSpeci?cation,the driving factors that are the justi?cations of the changes in the product family.Requirement,Regulation,and Technology are the subclasses of DevelopmentSpeci?cation currently supported.
4.Further research needs
A number of issues have to be investigated before implementation of a PLM system support
and
Fig.10.Product and component
families.
Fig.11.Family evolution.
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interoperability platform based on the proposed product information-modeling framework can begin.First,the framework presented is but a ?rst step towards a complete product modeling architecture supporting the PLM concept.A search needs to be made to identify other framework components that need to be modeled and integrated.
Second,a focused search of the PLM literature and current PLM system products needs to be made so as to clarify all product information needs throughout the PLM process to develop a conceptual Application Programming Interface (API)that can serve all product information to all PLM process components.As part of such a conceptual interface speci?cation,considerable attention needs to be given to the possible interactions between the product data served by the framework and metadata about the product data maintained by the PLM system.
Third,recognizing that product information modeling frameworks of the scope contemplated here will be heterogeneous,rather than single-language,single-vendor homogeneous systems,research is needed to identify,and if necessary develop,information exchange standards that can provide the degree of interoperability that will be necessary.
5.Conclusions
Until quite recently,computer support for product development tended to cover a narrow slice of a product’s lifecycle,typically the segment from the product’s engin-eering speci?cation to its physical embodiment.The PLM concept promises to provide support for the product’s entire lifecycle,from the ?rst conceptualization to the disposal of
its last instance.The volume,diversity,and complexity of information describing the product will increase correspondingly.
This paper makes a proposal for a single PLM system support framework for product information that can access,store,serve,and reuse all the product information through-out the entire lifecycle.The guiding principles for such a framework are outlined,and four components that constitute the kernel of such a framework are described.Further research is needed to identify and model the other components of the framework,to develop a conceptual API between PLM systems and the framework,and to identify or develop standards for the information inter-change.The proposed product information modeling architecture framework is contemplated to have a broader scope than just being a product information server to PLM systems.Design and manufacturing process components interoperate by exchanging large volumes of product information,and the proposed product information model-ing framework needs to support such ‘horizontal’infor-mation exchanges as readily as the ‘vertical’exchanges among process components,PLM systems and any inter-mediary systems,such as PDM and Enterprise Resource Planning (ERP)systems.
6.Disclaimer
No approval or endorsement of any commercial product by the National Institute of Standards and Technology is intended or implied.Certain commercial equipments,instruments,or materials are identi?ed in this report
in
Fig.12.Rationale.
R.Sudarsan et al./Computer-Aided Design 37(2005)1399–14111409
order to facilitate better understanding.Such identi?cation does not imply recommendations or endorsement by the National Institute of Standards and Technology,nor does it imply the materials or equipment identi?ed are necessarily the best available for the purpose.
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Sudarsan Rachuri is a Research Professor
with the Department of Engineering Manage-
ment,George Washington University,
Washington DC.He is a Guest Researcher in
the Design and Process Group,Manufacturing
Systems Integration Division,National Insti-
tute of Science and Technology(NIST),
Gaithersburg,MD.Presently,his work at
NIST includes development of information
models for product lifecycle management,
assembly models and system level tolerancing, and standards development.He coordinates research projects with industry and academia.He closely works with various standard bodies including ISO TC184/SC4.He is a member of ASME Y14.5.1and Advisory Group Member for ISO/TC213/AG12,Mathematical Support for GPS.He is the regional editor(North America)for the International Journal of Product Development,and associate editor for International Journal of Product Lifecycle Management.His areas of interest include scienti?c computing, mathematical modeling,product lifecycle management,ontology model-ing,system level tolerancing,quality,object oriented modeling,and knowledge engineering.Rachuri Sudarsan received the MS and PhD degrees from the Indian Institute of Science,
Bangalore.
Steven J.Fenves is University Professor
Emeritus of Civil and Environmental Engin-
eering at Carnegie Mellon University and is a
Guest Researcher at NIST.He received his
degrees in Civil Engineering from the Univer-
sity of Illinois and has taught at the University
of Illinois,Carnegie Mellon,MIT,National
University of Mexico,Cornell and Stanford.
His research deals with computer-aided engin-
eering,design standards,engineering data-
bases,and structural analysis and design environments.He is the author of six books and over300articles and is a member of the National Academy of Engineering and an Honorary Member of the American Society of Civil Engineers.
R.Sudarsan et al./Computer-Aided Design37(2005)1399–1411 1410
Ram D.Sriram,Senior Member IEEE is
currently leading the Design and Process group
in the Manufacturing Systems Integration
Division at the National Institute of Standards
and Technology,where he conducts research
on standards for interoperability of computer-
aided design systems and on healthcare infor-
matics.Prior to that he was on the engineering
faculty(1986–1994)at the Massachusetts
Institute of Technology(MIT)and was instru-
mental in setting up the Intelligent Engineering Systems Laboratory.At MIT,Sriram initiated the MIT-DICE project, which was one of the pioneering projects in collaborative engineering. Sriram has co-authored or authored more than175papers,books,and reports in computer-aided engineering,including thirteen books.Sriram was a founding co-editor of the International Journal for AI in Engineering. In1989,he was awarded a Presidential Young Investigators Award from the National Science Foundation,USA.Sriram has a BS from IIT,Madras, India,and an MS and a PhD from Carnegie Mellon University,Pittsburgh, USA.Fujun Wang has worked on the research and development of collaborative design for10years.He is now working as a system engineer at the Shared Service Group,the Boeing company.Before joining Boeing,he had worked as a guest researcher for4years at the Manufacturing Systems Integration Division,National Institute of Standards and Technology.Dr Wang had worked at the Automation and Robotics Research Institute,University of Texas at Arlington,and the Key Center of Design Computing,University of Sydney,Australia during1998to2000.Dr Wang received his PhD from the Beijing University of Aeronautics and Astronautics,China,in1997.
R.Sudarsan et al./Computer-Aided Design37(2005)1399–14111411
信息技术试卷----难题 一、选择题 1、目前计算机上最常用的外存储器是（）。 A．打印机 B.数据库 C.磁盘 D.数据库管理系统 2、计算机的系统软件与应用软件的相互作用是（）。 A.前者以后者为基础 B.后者以前者为基础 C.互不为基础 D.互为基础 3、微机使用的内存RAM中存储的数据在断电后（）丢失。 A.不会 B.部分 C.完全 D. 有时 4、通常，一个汉字和一个英文字符在计算机中存储所占字节数的比例为（）。 A.4：1 B.2：1 C.1：1 D.1：2 5、计算机病毒对于操作计算机的人（）。 A.只会感染，不会致病 B.会感染致病，但无严重危害 C.不会感染 D.产生的作用尚不清楚 6、计算机外存储器中存放的数据，在正常情况下，断电后（）丢失。 A.不会 B.少量 C.完全 D.不一定 7、当软盘处于写保护时，（）。 A.既能读又能写 B. 既不能读又不能写 C.只能读不能写 D.不能读但能写 8、（）键的功能是取消当前操作。 A.Enter B.Alt C.Esc D.Ins 9、办公自动化是计算机的一项应用，它属于计算机的（）方面的应用。A.数据处理 B.科学计算 C.实时控制 D.辅助设计 10、一只软盘只能进行读取操作，一般情况下（）。 A.病毒不能侵入 B.病毒能侵入 C.能够向里面存入信息 D.能修改里面的文件 11、通常所说的内存容量主要是指（）的容量。 A.CPU B.ROM C.RAM D.128MB 12、下列不属于操作系统的是（）。 A.Unix B.Windows95 C.Word D.MS-DOS 13、对于计算机裸机来说，首先必须安装的软件是（）。 A.画图软件 B.应用软件 C.文字处理软件 D.操作系统软件 14、若想关闭计算机，可以按（）组合键。 A.Alt+F4 B.Ctrl+F4 C.Esc D.Ctrl+Alt+Del 15、在Windows98中，下列文件名不合法的是（）。 A.练习题.DOC B.aBc C.How are you D.hello*.* 16、若要给一个文件夹重命名，可以先选中该文件，然后按（）键。 A.F1 B.F2 C.F3 D.Del 17、对文件重命名后，文件的内容（）。
《计算机组成原理》模拟试卷十六 一.填空题（每空1分，共20分） 1.计算机系统是一个由硬件、软件组成的多级层次结构。它通常由 A.______、 B.______、 C.______、汇编语言级、高级语言级组成。每一级上都能进行 D.______。 2.为了运算器的高速性，采用了A.______进位、B.______乘除法、C.______等并行 技术措施。 3.奔腾CPU中，L2级cache的内容是A.______的子集，而B.______的内容又是 C.______的子集。 4.RISC指令系统的最大特点是 A.______、B.______固定、C.______种类少、只有 D.______指令访问存储器。 5.当代流行的标准总线追求与A.______、B.______、C.______无关的开发标准。 6.SCSI是处于A.______和B.______之间的并行I/O接口，可允许连接C.______台不 同类型的高速外围设备。 二. 选择题（每题1分，共20分） 1.邮局把信件进行自动分拣，使用的计算机技术是______。 A. 机器翻译 B. 自然语言理解 C. 机器证明 D. 模式识别 2.下列数中最大数为______。 A. （101001）2 B. （52）8 C. （13）16 D. （101001）BCD 3.某机字长16位，定点表示，尾数15位，数符1位，则定点法原码整数表示的最大 正数为______ A. （215-1）10 B. -（215-1）10 C. （1-2-15）10 D. -（1-2-15）10 4.算术/逻辑运算单元74181ALU可完成______。 A.16种算术运算和16种逻辑运算功能 B.16种算术运算和8种逻辑运算功能 C.8种算术运算和16种逻辑运算功能 D.8种算术运算和8种逻辑运算功能 5.某计算机字长16位，其存储容量为2MB，若按半字编址，它的寻址范围是______。 A. 8M B. 4M C. 2M D. 1M 6.磁盘存储器的等待时间通常是指______。 A. 磁盘旋转半周所需的时间 B. 磁盘转2/3周所需时间 C. 磁盘转1/3周所需时间 D. 磁盘转一周所需时间 7.下列有关存储器的描述中，不正确的是______。 A.多体交叉存储器主要解决扩充容量问题 B.访问存储器的请求是由CPU发出的 C.cache与主存统一编址，即主存空间的某一部分属于cache D.cache的功能全由硬件实现 8.常用的虚拟存储器系统由______两级存储器组成，其中辅存是大量的磁表面存储
1.已知x和y，用变形补码计算x+y，同时指出结果是否溢出（每题6分，共18分） （1）x=11011，y=00011 （2）x=11011，y=-10101 （3）x=-10110，y=-00001 2.指令格式结构如下所示，试分析指令格式及寻址方式特点。（10分） 31 25 24 23 20 19 0 3.CPU执行一段程序时，CACHE完成存取的次数为5000次，主存完成存取的次数为200次。已知CACHE存取周期为40ns，主存存取周期为160ns。分别求CACHE的命中率H、平均访问时间Ta和CACHE-主存系统的访问效率e （12分） 4. 有一个１６K×16位的存储器，由1K×4位的DRAM芯片构成（芯片是64×64结构）。问：（每题5分，共15分） (1)共需要多少RAM芯片？ (2)采用异步刷新方式，如单元刷新间隔不超过２ms，则刷新信号周期是多少 (3)如采用集中刷新方式，存储器刷新一遍最少用多少读／写周期？死时间率是多少？5.用512K*16位的FLASH存储器芯片组成一个2M*32的半导体只读存储器，试问：（每题5分，共20分） (1）数据寄存器多少位？ (2）地址寄存器多少位？ (3）共需要多少个这样的器件？ (4）画出此存储器的组成框图. 6.设有一个cache的容量为2K字，每块16个字，问：（每题5分，共25分） （1）cache中可容纳多少个块？ （2）若主存的容量是256K字，主存可分多少块？ （3）主存地址有多少位，cache的地址有多少位？ （4）在直接映射方式中，主存中第135块映射到cache中哪一块？ （5）进行地址映射时，主存地址分为几段，各段有多少位？ 答案 2.操作码：定长操作码，可表示128条指令；操作数：双操作数，可构成RS或SS型指令，有直接、寄存器、寄存器间接寻址方式，访存范围1M，可表示16个寄存器。 3. H=Nc/(Nc+Nm)=5000/5200≈0.96 Ta=Tc+(1-H)×Tm=40ns+(1-0.96) ×160ns=46.4ns E=Tc/Ta=40ns/46.4ns×100%=86.2% 4.（1）存储器的总容量为16K×16位=256K位，所以用DRAM芯片为1K×4位=4K位 故芯片总数为：256K位/4K位= 64片 （2）采用异步刷方式，在2ms时间内分散地把芯片64行刷新一遍，故刷新信号的时间间隔为2ms/64 = 31.25μs，即可取刷新信号周期为30μs。 （3）如采用集中刷新方式，假定T为读/写周期，如16组同时进行刷新，则所需刷新时间为64T。设T单位为μs，2ms=2000μs，则死时间率=（64T/2000）×100%。 5.（1）32；（2）21；（3）4*2=8；（4）
第3章存储系统 一．判断题 1．计算机的主存是由RAM和ROM两种半导体存储器组成的。 2．CPU可以直接访问主存，而不能直接访问辅存。 3．外（辅）存比主存的存储容量大、存取速度快。 4．动态RAM和静态RAM都是易失性半导体存储器。 5．Cache的功能全部由硬件实现。 6．引入虚拟存储器的目的是为了加快辅存的存取速度。 7．多体交叉存储器主要是为了解决扩充容量的问题。 8．Cache和虚拟存储器的存储管理策略都利用了程序的局部性原理。 9．多级存储体系由Cache、主存和辅存构成。 10．在虚拟存储器中，当程序正在执行时，由编译器完成地址映射。 二．选择题 1．主（内）存用来存放。 A．程序 B．数据 C．微程序 D．程序和数据 2．下列存储器中，速度最慢的是。 A．半导体存储器 B．光盘存储器 C．磁带存储器 D．硬盘存储器 3．某一SRAM芯片，容量为16K×1位，则其地址线有。 A．14根 B．16K根 C．16根 D．32根 4．下列部件（设备）中，存取速度最快的是。 A．光盘存储器 B．CPU的寄存器 C．软盘存储器 D．硬盘存储器 5．在主存和CPU之间增加Cache的目的是。 A．扩大主存的容量 B．增加CPU中通用寄存器的数量 C．解决CPU和主存之间的速度匹配 D．代替CPU中的寄存器工作 6．计算机的存储器采用分级存储体系的目的是。 A．便于读写数据 B．减小机箱的体积 C．便于系统升级 D．解决存储容量、价格与存取速度间的矛盾 7．相联存储器是按进行寻址的存储器。 A．地址指定方式 B．堆栈存取方式 C．内容指定方式 D．地址指定与堆栈存取方式结合 8．某SRAM芯片，其容量为1K×8位，加上电源端和接地端后，该芯片的引出线的最少数目应为。 A．23 B．25 C．50 D．20 9．常用的虚拟存储器由两级存储器组成，其中辅存是大容量的磁表面存储器。 A．主存—辅存 B．快存—主存 C．快存—辅存 D．通用寄存器—主存 10．在Cache的地址映射中，若主存中的任意一块均可映射到Cache内的任意一快的位置上，则这种方法称为。 A．全相联映射 B．直接映射 C．组相联映射 D．混合映射 三．填空题
一、选择题 1、存储器和CPU之间增加Cache的目的是( )。 A. 增加内存容量 B. 提高内存的可靠性 C. 解决CPU与内存之间速度问题 D.增加内存容量，同时加快存取速度 2、常用的虚拟存储系统由（）两级存储器组成，其中辅存是大容量的磁表面存储器。 A 主存-辅存 B 快存-主存 C 快存-辅存 D 通用寄存器-主存 3、双端口存储器所以能高速进行读/ 写，是因为采用（）。A．高速芯片B．两套相互独立的读写电路 C．流水技术D．新型器件 4、在下列几种存储器中，CPU可直接访问的是（）。 A. 主存储器 B. 磁盘 C. 磁带 D. 光盘 5、SRAM芯片，存储容量为64K×16位，该芯片的地址线和数据线数目为（）。 A．64，16 B．16，16 C．64，8 D．16，64。 6、采用虚拟存储器的主要目的是（）。 A．扩大主存储器的存储空间，并能进行自动管理和调度B．提高主存储器的存取速度 C．提高外存储器的存取速度 D．扩大外存储器的存储空间
7、双端口存储器在（）情况下会发生读/写冲突。 A. 左端口与右端口的地址码不同 B. 左、右端口的地址码相同 C. 左、右端口的数据码相同 D. 左、右端口的数据码不同 8、计算机系统中的存储器系统是指（）。 A RAM存储器 B ROM存储器 C 主存储器D主存储器和外存储器 9、某计算机字长32位，其存储容量为4MB，若按半字编址，它的寻址范围是（）。 A 0~4MB-1 B 0~2MB-1 C 0~2M-1 D 0~1M-1 10、某一SRAM芯片，采用地址线与数据线分离的方式，其容量为512×8位，除电源和接地端外，该芯片引出线的最小数目应是（）。 A 23 B 25 C 50 D 19 11、以下四种类型的半导体存储器中，以传输同样多的字为比较条件，则读出数据传输率最高的是（）。 A DRAM B SRAM C FLASH ROM D EPROM 12、计算机的存储器采用分级存储体系的目的是（）。A．便于读写数据B．减小机箱的体积
计算机组成原理 第1章计算机系统概论 一.填空题 1. 计算机系统是由硬件和软件两大部分组成的，前者是计算机系统的物质基础，而后者则是计算机系统解题的灵魂，两者缺一不可。 2. 存储程序是指解题之前预先把程序存入存储器；程序控制是指控制器依据所存储的程序控制计算机自动协调地完成解题的任务，这两者合称为存储程序控制，它是冯·诺依曼型计算机的重要工作方式。 3.通常将控制器和运算器合称为中央处理器(CPU) ；而将控制器、运算器和内存储器合称为计算机的主机。 4.计算机系统的硬件包括控制器、运算器、存储器、I/O接口和I/O设备等五大部分。 二.选择题 1. 指令周期是指（ C ）。 A.CPU从主存取出一条指令的时间 B.CPU执行一条指令的时间 C. CPU从主存取出一条指令加上执行该指令的时间 三.问答题 1.存储程序控制是冯?诺依曼型计算机重要的工作方式，请解释何谓存储程序、程序控制？ 答：存储程序是指将解题程序(连同原始数据)预先存入存储器； 程序控制是指控制器依据存储的程序，控制全机自动、协调的完成解题任务。 2.计算机系统按功能通常可划分为哪五个层次？画出其结构示意图加以说明。 答：.五级组成的计算机系统如图1.7 (课本P18) 1）微程序设计级：微指令直接由硬件执行。 2）一般机器级(机器语言级)：由微程序解释机器指令系统，属硬件级。 3）操作系统级：由操作系统程序实现。 4）汇编语言级：由汇编程序支持执行。 5）高级语言级：由高级语言编译程序支持执行。 这五级的共同特点是各级均可编程。 四.计算题 1.设某计算机指令系统有4种基本类型的指令A、B、C和D，它们在程序中出现的频度(概率)分别为0.3、0.2、0.15和0.35，指令周期分别为5ns、5.5ns、8ns和10ns，求该计算机的平均运算速度是多少MIPS(百万条指令每秒)？ 解:指令平均运算时间： T=5×0.3＋5.5×0.2＋8×0.15＋10×0.35＝7.3 (ns) 平均运算速度： V=1/T=1/(7.3×10－3)＝137(MIPS) 第2章运算方法与运算器 一.填空题 1.若某计算机的字长是8位，已知二进制整数x＝10100，y＝–10100，则在补码的表示中，[x]补＝00010100 ，[y]补＝11101100 。 2. 若浮点数格式中阶码的基数已确定，而且尾数采用规格化表示法，则浮点数表示的数，其范围取决于浮点数阶码的位数，而精度则取决于尾数的位数。
纠结了这么久，现在总算有点儿头绪了，先把它整理到这里先，有几点还是j经常被弄糊涂：地址和数据，地址/数据复用，地址的计算，总线的概念，执行指令跟脉冲的关系，哎呀呀，看来计算机组成和原理不看不行啊，得找个时间瞧瞧，过把瘾了解了解。。。 使用ALE信号作为低8位地址的锁存控制信号。以PSEN信号作为扩展程序存储器的读选通信号，在读外部ROM是PSEN是低电平有效，以实现对ROM 的读操作。 由RD和WR信号作为扩展数据存储器和I/O口的读选通、写选通信号。 ALE/PROG: 当访问外部存储器时，地址锁存允许的输出电平用于锁存地址的地位字节。 在FLASH编程期间，此引脚用于输入编程脉冲。 在平时，ALE端以不变的频率周期输出正脉冲信号，此频率为振荡器频率的1/6。因此它可用作对外部输出的脉冲或用于定时目的。然而要注意的是：每当用作外部数据存储器时，将跳过一个ALE脉冲。如想禁止ALE的输出可在SFR8EH地址上置0。此时，ALE只有在执行MOVX，MOVC指令是ALE才起作用。另外，该引脚被略微拉高。如果微处理器在外部执行状态ALE禁止，置位无效。 当访问外部存储器时，ALE作为锁存扩展地址的低8位字节的控制信号。 当访问外部数据存储器时，ALE以十二分之一振荡频率输出正脉冲，同时这个引脚也是EPROM编程时的编程脉冲输入端。] 当非访问外部数据存储器时，ALE以六分之一振荡频率固定输出正脉冲，8051一个机器周期=6个状态周期=12个振荡周期，若采用6MHz的晶体振荡器，则ALE会发出1MHz的固定的正脉冲。因此它可以用来做外部时钟或定时。如果我们把这个功能应用与实际，可能给我们的设计带来简化，降低生产成本。 ALE脚是在使用MOVX、MOVC指令时才会变成有效（这些指令都使用到外部RAM或ROM 的地址。这些指令都有一个特点：地址和数据分时出现在P0口）。使用Ｃ写程序时，要使用它有效，可用访问内部RAM地址的方法。如：uVariable=*((char *)0x12C),把0x12C地址的内容给uVariable变量。这个过程有效的脚为ALE、RD。 这个信号线的信号生成是MCU硬件电路实现的，不可以人工控制。 在某些内置TOM的MCU里，可以关闭ALE信号输出，以降低EMI。
第1章计算机系统概论 5. ?诺依曼计算机的特点是什么？ 解：?诺依曼计算机的特点是：P8 (1)计算机由运算器、控制器、存储器、输入设备、输出设备五大部件组成； (2)指令和数据以同同等地位存放于存储器，并可以按地址访问； (3)指令和数据均用二进制表示； (4)指令由操作码、地址码两大部分组成，操作码用来表示操作的性质，地址码 用来表示操作数在存储器中的位置； (5)指令在存储器中顺序存放，通常自动顺序取出执行； (6)机器以运算器为中心（原始?诺依曼机）。 7. 解释下列概念：主机、CPU、主存、存储单元、存储元件、存储基元、存储元、存储字、存储字长、存储容量、机器字长、指令字长。 解：课本P9-10 (1)主机：是计算机硬件的主体部分，由CPU和主存储器MM合成为主机。 (2)CPU：中央处理器，是计算机硬件的核心部件，由运算器和控制器组成；（早 期的运算器和控制器不在同一芯片上，现在的CPU除含有运算器和控制器外还集成了Cache）。 (3)主存：计算机中存放正在运行的程序和数据的存储器，为计算机的主要工作 存储器，可随机存取；由存储体、各种逻辑部件及控制电路组成。 (4)存储单元：可存放一个机器字并具有特定存储地址的存储单位。 (5)存储元件：存储一位二进制信息的物理元件，是存储器中最小的存储单位， 又叫存储基元或存储元，不能单独存取。 (6)存储字：一个存储单元所存二进制代码的逻辑单位。 (7)存储字长：一个存储单元所存储的二进制代码的总位数。 (8)存储容量：存储器中可存二进制代码的总量；（通常主、辅存容量分开描述）。 (9)机器字长：指CPU一次能处理的二进制数据的位数，通常与CPU的寄存器位 数有关。 (10)指令字长：机器指令中二进制代码的总位数。 8. 解释下列英文缩写的中文含义：CPU、PC、IR、CU、ALU、ACC、MQ、X、MAR、
计算机组成原理题解指南 第一部分：简答题 第一章计算机系统概论 1．说明计算机系统的层次结构。 计算机系统可分为：微程序机器级，一般机器级（或称机器语言级），操作系统级，汇编语言级，高级语言级。 第四章主存储器 1．主存储器的性能指标有哪些？含义是什么？ 存储器的性能指标主要是存储容量. 存储时间、存储周期和存储器带宽。 在一个存储器中可以容纳的存储单元总数通常称为该存储器的存储容量。 存取时间又称存储访问时间，是指从启动一次存储器操作到完成该操作所经历的时间。 存储周期是指连续两次独立的存储器操作（如连续两次读操作）所需间隔的最小时间。 存储器带宽是指存储器在单位时间中的数据传输速率。 2．DRAM存储器为什么要刷新？DRAM存储器采用何种方式刷新？有哪几种常用的刷新方式？ DRAM存储元是通过栅极电容存储电荷来暂存信息。由于存储的信息电荷终究是有泄漏的，电荷数又不能像SRAM存储元那样由电源经负载管来补充，时间一长，信息就会丢失。为此必须设法由外界按一定规律给栅极充电，按需要补给栅极电容的信息电荷，此过程叫“刷新”。 DRAM采用读出方式进行刷新。因为读出过程中恢复了存储单元的MOS栅极电容电荷，并保持原单元的内容，所以读出过程就是再生过程。 常用的刷新方式由三种：集中式、分散式、异步式。 3．什么是闪速存储器？它有哪些特点？ 闪速存储器是高密度、非易失性的读/写半导体存储器。从原理上看，它属于ROM型存储器，但是它又可随机改写信息；从功能上看，它又相当于RAM，所以传统ROM与RAM的定义和划分已失去意义。因而它是一种全新的存储器技术。 闪速存储器的特点：（1）固有的非易失性，（2）廉价的高密度，（3）可直接执行，（4）固态性能。4．请说明SRAM的组成结构，与SRAM相比，DRAM在电路组成上有什么不同之处？ SRAM存储器由存储体、读写电路、地址译码电路、控制电路组成，DRAM还需要有动态刷新电路。 第五章指令系统 1．在寄存器—寄存器型，寄存器—存储器型和存储器—存储器型三类指令中，哪类指令的执行时间最长？哪类指令的执行时间最短？为什么？ 寄存器-寄存器型执行速度最快,存储器-存储器型执行速度最慢。因为前者操作数在寄存器中，后者操作数在存储器中，而访问一次存储器所需的时间一般比访问一次寄存器所需时间长。 2．一个较完整的指令系统应包括哪几类指令？ 包括：数据传送指令、算术运算指令、逻辑运算指令、程序控制指令、输入输出指令、堆栈指令、字符串指令、特权指令等。 3．什么叫指令？什么叫指令系统？ 指令就是要计算机执行某种操作的命令 一台计算机中所有机器指令的集合，称为这台计算机的指令系统。 第六章中央处理部件CPU 1．指令和数据均存放在内存中，计算机如何从时间和空间上区分它们是指令还是数据。 时间上讲，取指令事件发生在“取指周期”，取数据事件发生在“执行周期”。从空间上讲，从内存读出的指令流流向控制器（指令寄存器）。从内存读出的数据流流向运算器（通用寄存器）。 2．简述CPU的主要功能。 CPU主要有以下四方面的功能：(1)指令控制程序的顺序控制，称为指令控制。 (2)操作控制 CPU管理并产生由内存取出的每条指令的操作信号，把各种操作信号送往相应部件，从而 控制这些部件按指令的要求进行动作。 (3)时间控制对各种操作实施时间上的控制，称为时间控制。 (4)数据加工对数据进行算术运算和逻辑运算处理，完成数据的加工处理。 3．举出CPU中6个主要寄存器的名称及功能。 CPU有以下寄存器： (1)指令寄存器（IR）：用来保存当前正在执行的一条指令。 (2)程序计数器（PC）：用来确定下一条指令的地址。 (3)地址寄存器（AR）：用来保存当前CPU所访问的内存单元的地址。
综合题 1. 设存储器容量为32字，分为M0-M3四个模块，每个模块存储8个字，地址分配方案分别如下图中图（a）和图（b）所示。 （1）（a）和（b）分别采用什么方式进行存储器地址编址？ （2）设存储周期T=200ns，数据总线宽度为64位，总线传送周期τ=50ns。问(a)和（b）两种方式下所对应的存储器带宽分别是多少(以Mb/s为单位)？ 2．假设某机器有80条指令，平均每条指令由4条微指令组成，其中有一条取指微指令是所有指令公用的，已知微指令长度为32位，请估算控制存储器的容量是多少字节？ 3. （1）用16K×8位的SRAM芯片形成一个32K×16位的RAM区域，共需SRAM芯片多少片？ （2）设CPU地址总线为A15～A0，数据总线为D15～D0，控制信号为R/W（读/写）、MREQ（允许访存）。SRAM芯片的控制信号有CS和WE。要求这32K×16位RAM 区域的起始地址为8000H，请画出RAM与CPU的连接逻辑框图。
*4 CPU执行一段程序时，Cache完成存取的次数为3800次，主存完成存取的次数为200次，已知Cache存取周期为50ns，主存为250ns， 求（1）Cache命中率。（2）平均访问时间（3）Cache/主存系统的效率。 5．已知某机采用微程序控制方式，其控制存储器容量为512*48（位）。微程序可在整个存储器中实现转移，可控制微程序转移的条件共4个，微指令采用水平型格式，后继微指令地址采用断定方式，如下图所示。 （1）微指令中的三个字段分别应为多少位？ （2）画出围绕这种微指令格式的微程序控制器逻辑框图。 6．用2M×8位的SRAM芯片，设计4M×16位的SRAM存储器，试画出存储器芯片连接图。 *7．某计算机系统的内存储器由cache和主存构成，cache的存储周期为30ns，主存的存取周期为150ns。已知在一段给定的时间内，CPU共访问内存5000次，其中400次访问主存。问： ① cache的命中率是多少？ ② CPU访问内存的平均时间是多少纳秒？
淮海工学院计算机科学系实验报告书 课程名：《操作系统》 题目：虚拟存储器管理 页面置换算法模拟实验 班级： 学号： 姓名：
一、实验目的与要求 1.目的： 请求页式虚存管理是常用的虚拟存储管理方案之一。通过请求页式虚存管理中对页面置换算法的模拟，有助于理解虚拟存储技术的特点，并加深对请求页式虚存管理的页面调度算法的理解。 2.要求： 本实验要求使用C语言编程模拟一个拥有若干个虚页的进程在给定的若干个实页中运行、并在缺页中断发生时分别使用FIFO和LRU算法进行页面置换的情形。其中虚页的个数可以事先给定（例如10个），对这些虚页访问的页地址流（其长度可以事先给定，例如20次虚页访问）可以由程序随机产生，也可以事先保存在文件中。要求程序运行时屏幕能显示出置换过程中的状态信息并输出访问结束时的页面命中率。程序应允许通过为该进程分配不同的实页数，来比较两种置换算法的稳定性。 二、实验说明 1．设计中虚页和实页的表示 本设计利用C语言的结构体来描述虚页和实页的结构。 在虚页结构中，pn代表虚页号，因为共10个虚页，所以pn的取值范围是0—9。pfn代表实页号，当一虚页未装入实页时，此项值为-1；当该虚页已装入某一实页时，此项值为所装入的实页的实页号pfn。time项在FIFO算法中不使用，在LRU中用来存放对该虚页的最近访问时间。 在实页结构中中，pn代表虚页号，表示pn所代表的虚页目前正放在此实页中。pfn代表实页号，取值范围（0—n-1）由动态指派的实页数n所决定。next是一个指向实页结构体的指针，用于多个实页以链表形式组织起来，关于实页链表的组织详见下面第4点。 2．关于缺页次数的统计 为计算命中率，需要统计在20次的虚页访问中命中的次数。为此，程序应设置一个计数器count，来统计虚页命中发生的次数。每当所访问的虚页的pfn项值不为-1，表示此虚页已被装入某实页内， 此虚页被命中，count加1。最终命中率=count/20*100%。 3．LRU算法中“最近最久未用”页面的确定 为了能找到“最近最久未用”的虚页面，程序中可引入一个时间计数器countime，每当要访问 一个虚页面时，countime的值加1，然后将所要访问的虚页的time项值设置为增值后的当前
计算机组成原理试卷 及答案
计算机组成原理试题及答案 一、单项选择题（从下列各题四个备选答案中选出一个正确答案，并将其代号写在题干前面的括号内。） 1.若十进制数据为137.5则其八进制数为（B ）。 A、89.8 B、211.4 C、211.5 D、1011111.101 2.若x补=0.1101010，则x原=（A ）。 A、1.0010101 B、1.0010110 C、0.0010110 D、0.1101010 3.若采用双符号位，则发生正溢的特征是：双符号位为（ B）。 A、00 B、01 C、10 D、11 4.原码乘法是（A ）。 A、先取操作数绝对值相乘，符号位单独处理 B、用原码表示操作数，然后直接相乘 C、被乘数用原码表示，乘数取绝对值，然后相乘 D、乘数用原码表示，被乘数取绝对值，然后相乘 5.为了缩短指令中某个地址段的位数，有效的方法是采取（C）。 A、立即寻址 B、变址寻址 C、间接寻址 D、寄存器寻址 6.下列数中，最小的数是（A）。 A．(101001)2B．(52)８C．(2B)16D．45 7.下列数中，最大的数是（D）。 A．(101001)2B．(52)８C．(2B)16D．45 8.下列数中，最小的数是（D）。 A．（111111）2B．（72）８C．（2F）16D．50 9.已知：X=－0.0011，Y= -0.0101。（X+Y）补= ( A)。 Ａ．１．１１００Ｂ．１．１０１０
Ｃ．１．０１０１Ｄ．１．１０００ 10.一个512KB的存储器,地址线和数据线的总和是（C ）。 A．17 B．19C．27D．36 11.某计算机字长是16位它的存储容量是64KB,按字编址,它们寻址范围是（C ）。 A．64K B．32KB C．32K D．16KB 12.某一RAM芯片其容量为512*8位,除电源和接地端外该芯片引线的最少数目是 （C ）。 A.21 B.17 C.19 D.20 12.计算机内存储器可以采用（A）。 A.RAM和ROM B.只有ROM C.只有RAM D.RAM和SAM 13.单地址指令中为了完成两个数的算术操作，除地址码指明的一个操作数外，另一个数常需采用( C) 。 A.堆栈寻址方式 B.立即寻址方式 C.隐含寻址方式 D.间接寻址方式 14.零地址运算指令在指令格式中不给出操作数地址，因此它的操作数来自(B)。 A.立即数和栈顶 B.栈顶和次栈顶 C.暂存器和栈顶 D.寄存器和内存单元 15.指令系统中采用不同寻址方式的目的主要是( C)。 A.实现存储程序和程序控制 B.可以直接访问外存 C.缩短指令长度，扩大寻址空间，提高编程灵活性 D.提供扩展操作码的可能并降低指令译码难度 16.用于对某个寄存器中操作数的寻址方式称为( C)寻址。 A.直接 B.间接 C.寄存器直接 D.寄存器间接 17.寄存器间接寻址方式中，操作数处在( B )。 A.通用寄存器 B.贮存单元 C.程序计数器 D.堆栈 18.RISC是(A)的简称。
信息与管理科学学院计算机科学与技术 实验报告 课程名称：计算机组成原理 实验名称：存储器读写和总线控制实验 姓名：班级：指导教师：学号： 实验室：组成原理实验室 日期： 2013-11-22
一、实验目的 1、掌握半导体静态随机存储器RAM的特性和使用方法。 2、掌握地址和数据在计算机总线的传送关系。 3、了解运算器和存储器如何协同工作。 二、实验环境 EL-JY-II型计算机组成原理实验系统一套，排线若干。 三、实验内容 学习静态RAM的存储方式，往RAM的任意地址里存放数据，然后读出并检查结果是否正确。 四、实验操作过程 开关控制操作方式实验 注：为了避免总线冲突，首先将控制开关电路的所有开关拨到输出高电平“1”状态，所有对应的指示灯亮。 本实验中所有控制开关拨动，相应指示灯亮代表高电平“1”，指示灯灭代表低电平“0”。连线时应注意：对于横排座，应使排线插头上的箭头面向自己插在横排座上；对于竖排座，应使排线插头上的箭头面向左边插在竖排座上。 1、按图3－1接线图接线： 图3－1 实验三开关实验接线 2、拨动清零开关CLR，使其指示灯显示状态为亮—灭—亮。 3、往存储器写数据：
以往存储器的（FF ） 地址单元写入数据“AABB ”为例，操作过程如下： 4、按上述步骤按表3－2所列地址写入相应的数据 表3－2 5、从存储器里读数据： 以从存储器的（FF ） 地址单元读出数据“AABB ”为例，操作过程如下： (操作) (显示) (操作) (显示) (操作) (显6、按上述步骤读出表3－2数据，验证其正确性。 五、实验结果及结论 通过按照实验的要求以及具体步骤，对数据进行了严格的检验，结果是正确的，具体数据如图所示：
第一章 1）冯.诺依曼主要三个思想是什么？ （1）计算机处理采用二进制或二进制代码 （2）存储程序 （3）硬件五大部分：输入设备、输出设备、存储器、运算器和控制器 2）计算机硬件由哪5部分组成？ 输入设备、输出设备、存储器、运算器和控制器 3）VLSI中文的意思是什么？ 超大规模集成电路 4）列举出三个计算机应用领域？ 1．科学技术计算2．数据信息处理3．计算机控制 4．计算机辅助技术5．家庭电脑化 5）计算机系统分哪两大系统？ 硬件和软件系统 6）计算机内部信息包括哪两大信息？ 计算机中有两种信息流动：一是控制信息，即操作命令，其发源地为控制器；另一种是数据流，它受控制信息的控制，从一部件流向另一部件，边流动边加工处理。 7）计算机性能主要包括哪三个主要性能？ （1）基本字长: 是参与运算的数的基本长度，用二进制数位的长短来衡量，取决寄存器、加法器、数据总线等部件的位数。 （2）主存容量:可以用字节，有的用字长，K、M、G、T （3）运算速度: 是每秒能执行的指令条数来表示，单位是条/秒。（MIPS） 8）现代计算机系统分为五个层次级别是如何划分的？ 从功能上，可把现代计算机系统分为五个层次级别： 第一级是微程序设计级：是硬件级 第二级是一般机器级：机器语言级 第三级是操作系统级：是操作系统程序实现。(混合级) 第四级是汇编语言级：一种符号形式语言。 第五级是高级语言级 9）机器数是指什么？它主要是解决了数值的什么表示？ 10）机器数有哪4种表示方法？ 原码表示法、补码表示法、和移码表示法四种。 11）计算机数值有哪两种表示方式？它主要解决了数值的什么表示？ 定点表示和浮点表示。主要解决数中小数点的位置的确定。 12）浮点数在计算机内部表示两种方式是如何安排的？ 13）尾数是补码表示其规格化如何表示？ 正数：0.1×…×的形式负数：1.0×…×的形式 14）解释计算机内部数值0和字符0有何不同？ 数值0在计算机中为00H，而字符0为其ASCII码30H。 15）计算机如何判断加法溢出的？ 当运算结果超出机器所能表示的数域范围时，称为溢出。 判别方法有：符号位判别法、进位判别法、双符号位判别法。 16）半加器与全加器有什么不同？
《计算机组成原理》学科复习总结 ★第一章计算机系统概论 ?本章内容：本章主要讲述计算机系统的组成、计算机系统的分层结构、以及计算机的一些主要指标等 ?需要掌握的内容：计算机软硬件的概念，计算机系统的层次结构、体系结构和计算机组成的概念、冯.诺依曼的主要思想及其特点、计算机的主要指标 ?本章主要考点：概念 1、当前的CPU由那几部分组成组成？ 控制器、运算器、寄存器、cache (高速缓冲存储器) 2、一个完整的计算机系统应包括那些部分？ 配套的硬件设备和软件系统 3、什么是计算机硬件、计算机软件？各由哪几部分组成？它们之间有何联系？ 计算机硬件是指计算机的实体部分，它由看得见摸得着的各种电子元器件，各类光、电、机设备的实物组成。主要包括运算器(ALU)、控制器(CU)、存储器、输入设备和输出设备五大组成部分。软件是计算机程序及其相关文档的总称，主要包括系统软件、应用软件和一些工具软件。软件是对硬件功能的完善与扩充，一部分软件又是以另一部分软件为基础的再扩充。 4、冯·诺依曼计算机的特点 ●计算机由运算器、存储器、控制器、输入设备和输出设备五大部件组成 ●指令和数据以同等地位存于存储器内，可按地址寻访 ●指令和数据用二进制表示 ●指令由操作码和地址码组成，操作码用来表示操作的性质，地址码用来表示操作数在存储 器中的位置 ●指令在存储器内按顺序存放 ●机器以运算器为中心，输入输出设备和存储器间的数据传送通过运算器完成 5、计算机硬件的主要技术指标 ●机器字长：CPU 一次能处理数据的位数，通常与CPU 中的寄存器位数有关 ●存储容量：存储容量= 存储单元个数×存储字长；MAR（存储器地址寄存器）的位数 反映存储单元的个数，MDR（存储器数据寄存器）反映存储字长 主频 吉普森法 ●运算速度MIPS 每秒执行百万条指令 CPI 执行一条指令所需的时钟周期数 FLOPS 每秒浮点运算次数 ◎第二章计算机的发展及应用 ?本章内容：本章主要讲述计算机系统、微型计算机系统的发展过程以及应用。 ?需要掌握的内容：计算机的发展的不同阶段区分的方法、微型计算机发展中的区分、摩尔定律 ?本章主要考点：概念 1、解释摩尔定律
第五章虚拟存储器 一、单项选择题 1.虚拟存储器的最大容量＿＿＿。 *A. 为内外存容量之和 B. 由计算机的地址结构决定（（（实际容量 C. 是任意的 D. 由作业的地址空间决定 虚拟存储器是利用程序的局部性原理，一个作业在运行之前，没有必要全部装入内存，而只 将当前要运行那部分页面或段装入便可以运行，其他部分放在外部存储器内，需要时再从外 存调入内存中运行，首先它的容量必然受到外存容量的限制，其次寻址空间要受到计算机地 址总线宽度限制。最大容量（逻辑容量）收内外存容量之和决定，实际容量受地址结构决定。2．在虚拟存储系统中，若进程在内存中占 3 块（开始时为空），采用先进先出页面淘汰 算法，当执行访问页号序列为 1﹑ 2﹑ 3﹑ 4﹑ 1﹑2﹑ 5﹑ 1﹑ 2﹑ 3﹑4﹑ 5﹑ 6 时，将 产生＿＿＿次缺页中断。（开始为空，内存中无页面， 3 块物理块一开始会发生三次缺页。） A.7 B.8 C.9 3. 实现虚拟存储器的目的是＿＿＿ A. 实现存储保护 B. 实现程序浮动 D. 10 . C. 扩充辅存容 量 D. 扩充主存容量 4.作业在执行中发生了缺页中断, 经操作系统处理后 , 应让其执行＿＿＿指令 . （书本 158 页，（ 2）最后一句话） A. 被中断的前一条 B. 被中断 的 C. 被中断的后一 条 D. 启动时的第一条 5．在请求分页存储管理中，若采用FIFO 页面淘汰算法，则当分配的页面数增加时， 断的次数 ________。( 在最后一题做完后再作答)答案错误选择： D 缺页中 A．减少B. 增 加 C. 无影响 D. 可能增加也可能减少 6.虚拟存储管理系统的基础是程序的________理论 . A. 局部性 B. 全局 性 C. 动态 性 D. 虚拟性 7. 下述 _______页面淘汰算法会产生Belad y 现象 . A. 先进先出* B. 最近最少使 用 C. 最近不经常使 用 D. 最佳 所谓 Belady 现象是指：在分页式虚拟存储器管理中，发生缺页时的置换算法采用 FIFO（先 进先出）算法时，如果对—个进程未分配它所要求的全部页面，有时就会出现分配的页面 数增多但缺页率反而提高的异常现象。 二. 填空题 1.假设某程序的页面访问序列为1. 2. 3. 4. 5. 2. 3. 1. 2. 3. 4. 5. 1. 2. 3. 4 且开始执行时主 存中 没有页面，则在分配给该程序的物理块数是3 且采用 FIFO 方式时缺页次数是 ____13____; 在分配给程序的物理块数是 4 且采用 FIFO 方式时，缺页次数是 ___14______; 在分配给程序
第4章存储器 1. 解释概念：主存、辅存、Cache、RAM、SRAM、DRAM、ROM、PROM、EPROM、EEPROM、CDROM、Flash Memory。 答：主存：主存储器，用于存放正在执行的程序和数据。CPU可以直接进行随机读写，访问速度较高。 辅存：辅助存储器，用于存放当前暂不执行的程序和数据，以及一些需要永久保存的信息。 Cache：高速缓冲存储器，介于CPU和主存之间，用于解决CPU和主存之间速度不匹配问题。 RAM：半导体随机存取存储器，主要用作计算机中的主存。 SRAM：静态半导体随机存取存储器。 DRAM：动态半导体随机存取存储器。 ROM：掩膜式半导体只读存储器。由芯片制造商在制造时写入内容，以后只能读出而不能写入。 PROM：可编程只读存储器，由用户根据需要确定写入内容，只能写入一次。 EPROM：紫外线擦写可编程只读存储器。需要修改内容时，现将其全部内容擦除，然后再编程。擦除依靠紫外线使浮动栅极上的电荷泄露而实现。 EEPROM：电擦写可编程只读存储器。 CDROM：只读型光盘。 Flash Memory：闪速存储器。或称快擦型存储器。 2. 计算机中哪些部件可以用于存储信息？按速度、容量和价格/位排序说明。 答：计算机中寄存器、Cache、主存、硬盘可以用于存储信息。 按速度由高至低排序为：寄存器、Cache、主存、硬盘； 按容量由小至大排序为：寄存器、Cache、主存、硬盘；
按价格/位由高至低排序为：寄存器、Cache、主存、硬盘。 3. 存储器的层次结构主要体现在什么地方？为什么要分这些层次？计算机如何管理这些层次？ 答：存储器的层次结构主要体现在Cache-主存和主存-辅存这两个存储层次上。 Cache-主存层次在存储系统中主要对CPU访存起加速作用，即从整体运行的效果分析，CPU访存速度加快，接近于Cache的速度，而寻址空间和位价却接近于主存。 主存-辅存层次在存储系统中主要起扩容作用，即从程序员的角度看，他所使用的存储器其容量和位价接近于辅存，而速度接近于主存。 综合上述两个存储层次的作用，从整个存储系统来看，就达到了速度快、容量大、位价低的优化效果。 主存与CACHE之间的信息调度功能全部由硬件自动完成。而主存与辅存层次的调度目前广泛采用虚拟存储技术实现，即将主存与辅存的一部分通过软硬结合的技术组成虚拟存储器，程序员可使用这个比主存实际空间（物理地址空间）大得多的虚拟地址空间（逻辑地址空间）编程，当程序运行时，再由软、硬件自动配合完成虚拟地址空间与主存实际物理空间的转换。因此，这两个层次上的调度或转换操作对于程序员来说都是透明的。 4. 说明存取周期和存取时间的区别。 解：存取周期和存取时间的主要区别是：存取时间仅为完成一次操作的时间，而存取周期不仅包含操作时间，还包含操作后线路的恢复时间。即： 存取周期 = 存取时间 + 恢复时间 5. 什么是存储器的带宽？若存储器的数据总线宽度为32位，存取周期为200ns，则存储器的带宽是多少？ 解：存储器的带宽指单位时间内从存储器进出信息的最大数量。 存储器带宽= 1/200ns ×32位 = 160M位/秒 = 20MB/秒 = 5M字/秒 注意：字长32位，不是16位。（注：1ns=10-9s）
第五章外部存储器 [教学目标] 1．了解硬盘、光驱和软驱的基本结构。 2．掌握硬盘、光驱主从跳线的设置。 3．了解选购硬盘、光驱时要注意的问题。 [教学重点] 1、掌握硬盘型号的含义及读懂硬盘的标识。 2、掌握依据CPU合理选配主板的方法。 [教学难点] 掌握双硬盘的合理连接方法，以及区分不同接口的硬盘。 [分析学生] 学生对新购买的硬盘标出的容量和电脑检测出来的容量并不相符，容易产生疑惑。对DVD盘片与CD 盘片结构产生疑问。 [教学用具] 计算机，投影仪，已拆解的光驱和硬盘各一个。 [课时安排] 4课时 [教学过程] 一、导入新课 通过前面的学习，我们已经清楚断电后，内存中的信息就会丢失。完成保存信息的任务现阶段只能有硬盘、光盘这些外部存储设备完成。 提问学生：现今为什么硬盘、光盘成为了最主要的外部存储设备？ 引导学生思考、回答并相互补充。 教师总结归纳硬盘、光盘存储容量大、可靠性高、价格适中、技术成熟。因此它们在电脑中成为不可或缺的标准配置。 二、新课教学
第五章外部存储器 5.1硬盘存储器 5.1.1 基础知识：认识硬盘 提问：1同学们可能了解硬盘的外部模样，但我们现在请同学们仔细观察硬盘的内部结构之后，说一说硬盘是如何工作的？ 2硬盘内部是真空的么？ 学生思考、看书、回答； 教师总结： 第一个问题：硬盘由头盘组件与印刷电路板组件组成。磁头定位的驱动方式主要有步进电机驱动（已淘汰）和音圈电机驱动两种。其盘片及磁头均密封在金属盒中，构成一体，不可拆卸，金属盒内是高纯度气体。 在硬盘的正面都贴有硬盘的标签，标签上一般都标注与硬盘相关的信息，如产品型号、产地、出厂日期、产品序列号等。而硬盘的背面则是控制电路板，该板大都采用贴片式焊接，包括主轴调速电路、磁头驱动与伺服定位电路、读写电路、控制与接口电路等。在电路板上还有一块ROM芯片，里面固化的程序可以进行硬盘的初始化，执行加电和启动主轴电机，加电初始寻道、定位以及故障检测等。 第二个问题：因为根据硬盘的工作原理来分析，硬盘内部的磁头其实是处于悬浮状态的。而之所以会实现悬浮状态，其实是利用了空气流体动力学原理来实现的。如果硬盘的内部真空，那磁头悬浮的基本条件就被破坏了。实际上没有空气，磁头根本不能浮起来，也就无法工作。 ⑴硬盘接口类型 ①PATA接口 ②SATA接口 ⑵硬盘跳线 ⑶电源接口 ⑷硬盘数据线 5.1.2 硬盘技术指标 提问：硬盘的品牌繁多，一般在选购硬盘时都要参考一些主要的技术指标。同学们都了解哪些指标？学生思考、看书、回答； 教师总结： 硬盘的一些性能指标 1.主轴转速