Computer series

Introduction

The same scheme is adopted in the computer system structure, with program compatibility and standard input-output interfaces, which are a set of distances in performance and price Computer model.

Features

A computer series has the following five features.

①　The various models must be program compatible or upward compatible. Program compatibility means that programs compiled in machine language or assembly language can run on all models and get the same results. Due to the difference in performance of each model, such as the difference in computing speed, main memory capacity, or the type and quantity of peripheral equipment added, some programs can run on high-end models but not on low-end models. Programs that can run on low-end models can also run on high-end models. This kind of compatibility is called upward program compatibility. The program compatibility in the computer series enables several models to use the same system software. The application is also easy to move from one model to another.

②　 There is a unified system structure scheme among various models. They adopt a unified scheme in the machine's working mode, number and instruction format, instruction system, interrupt system, control and use mode of peripheral equipment, and man-machine exchange operation mode. This conceptual structure has nothing to do with the model, and the physical design and software design of each model do not violate the regulations of the system structure. From the programmer's point of view, these different models appear to be the same model.

③　 There is a regular arrangement of each model in a series in terms of performance and price. Only two or more models can form a series. Each model has a wide range of performances such as the computing speed of the central processing unit, the capacity of the main memory, the number of input-output channels, and the flow rate. Therefore, it can meet the needs of various users, and users need to update the machine due to the expansion of data processing capacity. Type requirements are conducive to expanding the market.

④　In addition to the unified system structure within the series, various standardized regulations are formulated and adopted in physical design, which is convenient for design, production and maintenance, and saves R&D investment. For example, the physical design of the standard interface between the peripheral equipment and the host is unified within the series, and is generally unified in the structural design of the cabinet, the size of the plug-in board, and the selection of connectors.

⑤　A series of machines designed according to a predetermined plan by a company or several companies or a design group can be called a series. The series of machines that are designed and produced to be compatible with other series of programs cannot be regarded as the same series. In addition to program compatibility, the series machines have other features. The design plan of each series machine should include its own design goals, model classification method, physical design standardization regulations, and market forecasts.

Generation and development

In the late 1950s, when computer production developed into a new industry, the serial design of computers came into being. There are two reasons for this. The first is the development of computer software. When computers became transistorized, their application areas expanded dramatically. In order to meet user requirements, various programming languages ​​have been produced one after another, and an operating system that can improve machine efficiency and reduce manual intervention becomes increasingly important. In the development of new models, the system software is relatively large, expensive, and has a long cycle, forcing designers to not equip each new model with a set of new system software, and adopt a set of the same for several models. System software. At the same time, the bigger reason for the emergence of series of machines is that users continue to request new machines with stronger processing capabilities. They believe that if the application software cannot run on the new model, it will cause significant losses, which prompts designers to design multiple models with different processing capabilities that can execute the same user program. This makes program compatibility the most important feature of the computer series. The second is that the cost of computer hardware is closely related to the level of processing power. Designers need to design multiple models with different performance indicators and therefore different prices to meet the different needs of various users.

The computer series appeared in the second generation of computers, but a clear concept was formed after IBM announced its third-generation computer product IBM-360 in 1964. IBM-360 is a universal series machine with program compatibility on the same system structure scheme. Since then, in addition to a small number of special-purpose computers, companies have organized design and production according to series of products.

In 1975, the first model compatible with the IBM-370 program appeared in the United States. In terms of computer development, a new type of plug-in compatible machine (PCM) has appeared, that is, choose a series that is considered the best in the market as the compatible object of your series, and design a series that can use that series according to the system structure of the selected series. The series of software. Strictly speaking, the plug-in compatible machine and the compatible series cannot be regarded as the same series machine. But from a software point of view, they are often generally regarded as the same series. The plug-in compatible machine was later understood as the program compatible machine. Since the 1970s, many computer manufacturers have turned to the design and production of plug-in compatible computers.

Design technology

The design technology of the computer series roughly includes five aspects.

After the system structure design decides to design a new series machine after market analysis, it is necessary to determine the design goal of the series machine, mainly to clarify its performance range, software and hardware main technical approaches, and general sales Price, what kind of products are ready to replace, and estimate the competitiveness with other products of the same period. This design goal is the basis for the system structure design.

The identity of the system structure is an important feature of a computer series. The design of the system structure must not only meet the requirements of software technology development, but also consider the cost of hardware implementation, technological advancement and reality. The final result of the design is the system structure design text, which is the basis for the design of system software and hardware personnel, and is basically the working principle of this series of machines.

Completing the system structure design is equivalent to conceptually forming a computer. The design of the system structure should specify all the machine attributes needed for the program design. ①Data word length and format: how many binary data words are, whether half-word length or double-word length is specified, whether there are variable-length numbers, how to specify fixed-point and floating-point numbers, and the encoding format of numbers. ②Instruction system: the binary number of basic instructions, instruction length, address selection method, and exact definition of each instruction. ③The working mode of the machine: It is stipulated that the machine has several working states. If a control word such as "program status word" is used to control the working mode of the machine, the control word needs to be clearly defined bit by bit. If it needs to be stored in the address memory, the number of the storage unit must also be specified. ④ Interrupt system: the arrangement of interrupt levels and their priority levels, the source signals that cause interrupts at all levels and the main actions of the interrupt process. ⑤The way of using peripheral equipment: Regardless of whether the peripheral equipment is used through the bus, channel or peripheral processor, a unified instruction must be specified, and the command for the operation of the peripheral equipment and the status information of the peripheral equipment must be specified. ⑥ Console: uniformly stipulate system console operations related to programming (such as initial program loading).

The system structure design work of the series machine has two characteristics. First, the system structure design of the series machine requires completeness and accuracy; the system structure design of the non-serial machine does not require the completeness and accuracy at the beginning, and can be continuously improved in the specific hardware design. The other is that the system structure design of the series machines must take into account the requirements of a wide range of hardware designs and operating systems of different sizes from low-end machines to high-end machines.

Model classification

There are at least two models in a series. When designing the series, consider how to classify the series. The purpose of binning is to adapt to the needs of different users and expand the coverage of the market. There are two main marks for binning: one is the difference in machine performance such as computing speed, main memory capacity, number of channels, and flow; the other is the difference in cost.

There are many ways to technically realize grading, and there are three main ones. ① Use different data path widths. For example, the width of the data path can be made into 64-bit, 32-bit or 16-bit, so that machine performance and manufacturing costs are separated. ② Use different control methods. For example, high-end machines use advanced operation, assembly line technology, and high-speed operation methods; while low-end machines use control methods that save equipment and tolerate longer operating times. ③ Use devices of different speeds. High-speed devices for high-end machines, medium and low-speed devices for low-end machines.

Functional test

Each series machine has its internal unified function test program, which has nothing to do with the hardware design of the machine. It has two functions: one is to check whether the machine conforms to the design of the system structure; the other is to check whether the programs are compatible between models. The test program must be able to check every aspect of the system's structural design, as well as every detail. Only through this test can the various functions of the machine meet the requirements. Only after passing this test can the system software be loaded. In this sense, the functional test program is the interface between hardware and software. The functional test procedure is different from the diagnostic procedure. The diagnostic program depends on the specific hardware design, and the fault location can be implemented using the diagnostic program. But passing the diagnostic program does not necessarily mean passing the functional test program. The functional test program is generated according to the actual situation of different models and different configurations to meet the requirements of use.

System software

The design and configuration of system software is the main content of series machine design. System software personnel must put forward requirements for the system structure design, and must strictly abide by the determined system structure design. For the user, he does not need to know the system structure and hardware design. System software is the outer layer of system structure and hardware design. A successful series machine must be equipped with a very complete system software, which should include several operating systems suitable for different user characteristics, several high-level languages, database management systems, communication and network control programs, and various standard subprogram packages.

System software compatibility does not mean simply using the software media. For different models in a series, even the same model, due to different configurations, the system software must be re-generated. Software is a commodity and must be purchased or rented. Many machines take measures to protect system software to prevent illegal copying of system software.

Hardware design

In addition to international standards and national standards, a company has its own corporate standards. In the design of the computer series, the design standards of this series of machines are formulated in combination with these three-level standards. The implementation of this standard can bring huge economic benefits to the design, production and maintenance of the series of machines.

The scope of these standards is very wide. In terms of components and devices, there are device selection and testing standards; in terms of mechanical structure design, there are different levels of assembly and interconnection standards; in terms of electrical performance, there are standards for circuit engineering application specifications; in terms of peripheral device interfaces, the host computer and The two-level interface between the peripheral device controllers and between the peripheral controller and the peripheral device adopts standardized conventions in almost every series, and these conventions will be stable for a long time.

These standardized features are fully reflected in the same series of models, but they are not absolute. Due to the rapid development of technology or due to the large coverage of a series, there may also be obvious inconsistencies in the mechanical structure design and circuit selection in the same series.

Outlook

Computer technology continues to develop, and the concept and design technology of the series will also change. The trend is: ① When the cost of the central processing unit hardware is much smaller than the cost of the software or the system, the series of computers may not be excessively divided in the hardware design of the central processing unit, but in a certain "building block" way Performance and peripheral equipment configuration are classified. ② While ensuring that the user program is compatible with the most important features of this series of machines, the manufacturer will also develop a variety of series machines with different concepts from traditional series machines, especially in micro and small computers.