Computer system architecture

Biological methodology in our everyday IT promises a kind of uniformity and interoperability that will encompass both medical and nonmedical computing, and mediation with implanted chips. This biology in IT is a methodology apart from neural nets, which are smart learning networks based on brain principles, represented in software. The changes of interest here are at the hardware level. It is probable that all traditional computer system architecture, medical and otherwise, will soon make the first steps to a transition to a deeper... 

On architecting computer systems for general application there are of course also many examples. Many concepts and terms about computer systems architecture can be found in the following ... 

Mano, M.M. 1993. Computer System Architecture. Prentice-HaU, Englewood Cliffs, NJ. 

The computer system architecture selected should provide the system interfaces specified by the computer system requirements and should implement the nonfunctional computer system requirements, such as those pertaining to performance and reliability. 

The more complex the computer system architecture, the more difficult it is to provide a safety demonstration. 

To reduce the potential for common cause failures, diversity should be incorporated into the computer system architecture to the extent necessary to achieve the safety and reliability requirements for the overall computer system. Equipment diversity means that different types of equipment are used to perform redundant functions. Functional diversity means that different methods are used to cany out a particular function. 

The documentation on the computer system design should contain a clear description of the computer system architecture selected. In addition, it should include a justification of the computer system design in terms of the required dependability of the system and the ability to implement all functional requirements. Such a justification can be provided, in part, by evidence of the use of a structured methodology. Also, the selected architecture should demonstrate a balance between simplicity in concept and the capacity to satisfy performance requirements. The justification of the computer system design can be partially achieved with the possible use of modelling and analysis, formal method iterations or prototyping. The results of such analyses should be described in the documentation on the computer system. 

Li, X., Gaudiot, J.-L. A compiler-assisted on-chip assigned-signature control flow checking. In Asia-Pacific Computer Systems Architecture Conference (2004)... 

Since biological systems can reasonably cope with some of these problems, the intuition behind neural nets is that computing systems based on the architecture of the brain can better emulate human cognitive behavior than systems based on symbol manipulation. Unfortunately, the processing characteristics of the brain are as yet incompletely understood. Consequendy, computational systems based on brain architecture are highly simplified models of thek biological analogues. To make this distinction clear, neural nets are often referred to as artificial neural networks. 

Direct digital control systems appeared in the mid-1980s and displaced older analog closed-loop schemes for temperature control. These digital systems improved both accuracy and reliability. The earlier systems were modeled after existing system architectures and did not contain intelligent, standalone field devices. There were numerous interfaces to the various building systems and the major decisions were made at a central computer. 

The concentration of all automation functions within a single computer (Section 7.19.1) may be possible for a very simple plant, but this type of configuration is inefficient for more complex processes for which there could be many thousands of connections between plant and computer. Currently, small industrial processes are controlled by a hierarchical architecture consisting of a central computer (usually a minicomputer), which is used to solve central automation problems, together with a series of peripheral computers (generally microprocessors which are called front-end computers) which control different sections of the plant (Fig. 7.104a). This type of architecture is termed a decentralised computer system. 

Smith et al., 1989] Smith, J., Jaffe, D., and Boyton, L. (1989). Music System Architecture on the NeXT Computer. In Pohlmann, K., editor, Audio in Digital Times, pages 301-312. Audio Engineering Society. 

Gordon, 1985] Gordon, J. W. (1985). System Architectures for Computer Music. 

Larger systems will typically beneht from a separate Architectural Design to explain the structure of the computer system and help link Fnnctional Specihcation to the Flardware and Software Design. For smaller and simpler compnter systems this information is more readily included in the Functional Specihcation. The Architectural Design will be required for the Design Review. 

Thereafter, Validation Plans should be updated or superseded by new plans when the architecture of the computer system changes from the original scope of validation there has been a significant change in how the computer system is used compared to the original vahdation there has been a change in operation and maintenance standards or when a revahdation exercise has been initiated. 

Architectural Designs should clearly identify the use of COTS software and hardware. Many modem computer systems make extensive use of COTS products. Architectural Designs should be included in the Requirements Traceability Matrix (RTM) as they will provide the vital linkage... 

Functional Testing is testing the system from a user s perspective — i.e., without knowledge of the internal architecture and structure of the system. Inventory checks are made by visual inspection, while functionality is verified by running the computer system. Test scenarios should include ... 

Revalidation does not necessarily imply a full repeat of the validation life cycle partial requalification is acceptable when justified. An analysis of changes implemented can be used to ho help determine how much revalidation is needed. Were there changes evenly spread throughout the system (sporadic) or were there focal points Computer systems with modular architectures may allow revalidation to be segregated to particular functional elements. 

Preventative maintenance concerns activities aimed at increasing the system s maintainability, such as updating documentation, adding conunents, and improving the modular structure (architecture) of the computer system. 

Distributed Computing An environment in which various tasks and resources are distributed among different computing systems (possibly from diiferent vendors) also used to refer to parallel computing on a distributed-memory architecture. 

Instruction Set Architecture—the abstract image of a computing system that is seen by a machine language (or assembly language) programmer. This inlcudes the instruction set, memory address modes, processor registers, and address and data formats. 

Finally, with the advent of high speed computers, parallel architecture, and the popularity of extended system methods, NEMD has seen yet another resurgence. Researchers are beginning to access the resources that allow one to compute the physical properties of real lubricants. The aim of this chapter is to provide the theoretical and technical foundations to enable simulators to model realistic systems under nonequilibrium conditions. 

Almost every computer made today uses some type of disk drive to store data and programs until they are needed. You ll learn the exact details of how they work later in Chapter 4, Disk System Architecture. Most drives need some kind of connection to the motherboard for the computer to talk to the disk drive. These connections are known as drive interfaces and there are two main types floppy drive interfaces and hard disk interfaces. Floppy disk interfaces allow floppy disk drives to be connected to the motherboard and, similarly, hard disk interfaces do the same for hard disks. When you see them on the motherboard, these interfaces are said to be on board, as opposed to being on an expansion card, known as off board. The interfaces consist of circuitry and a port. Most motherboards produced today include both the floppy disk and hard disk interfaces on the motherboard. 

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