Personal System PS / 2 of IBM (IBM Personal System / 2) is a family of personal computers a second generation of this small computer company. Family PS / 2 was first presented in April 1987, approximately six years after the release of IBM PC. The purpose of development of the PS / 2 - give users the opportunity to work with increased productivity while maintaining a high degree of compatibility with the software previously issued personal computers. In presenting the family of PS / 2 referred to the four different models. Each of these models: 30, 50, 60 and 80 may have the capacity, that of the model, the model 80 in line with higher levels of productivity. In following the April 1987 ad firm IBM has added five more models of the family of PS / 2: 25, 50Z, 55, 70 and R70. Currently, the model 25 is the youngest member of PS / 2. 50Z model and the model 55 may provide better performance than the model 60 and model 70 - higher performance than the model 80. Model 70 is the first portable model of a family of PS / 2. Despite the fact that, apparently, never a model system of PS / 2, in each system, PS / 2, regardless of the model will be at least the following components: a keyboard, system unit, which provides space for memory chips, boards of various adapters and devices, memory, monitor, printer. In all models, PS / 2, with the exception of model 25 and model R70, the main components are the modules, including a keyboard, a monitor and a printer connected to your system unit separate cables. Model 25 and Model R70 consists of the system unit and the monitor placed in one housing, which avoids the cable between the monitor and computer box. In April 1987, were represented by four models. Model 30 and Model 50 - This desktop device, each of which consists of a system unit placed horizontally on a table, and the monitor installed on the block. Model 60 and Model 80 have a system unit in a vertical design, which is installed on the floor. The keyboard and monitor in these models are placed on the table and connect the cable from standing on the floor box. Each member of a family of PS / 2 from IBM has a keyboard and system unit. There are systems in the type of monitor and the number and types of memory devices installed inside the system unit or connected to the cable. The success of IBM PC led to the adoption of the computer industry and business world as the de facto standard for personal computing technology. By adopting this standard, many wondered what the need in the second standard, presented a series of computers, which the company IBM has announced in April 1987 - a family of personal systems, PS / 2. Family PS / 2 differs from the PC series in several aspects, including the type of media used for storing data, supported the expansion connectors and the ability videostandarta. Although the difference is substantial, it is important to understand that both generations of personal computers are supported by DOS. Consequently, more than 99% of software developed for computers IBM PC, will work on a PS / 2. Once having seen the work of the software on the PS / 2, it is easy to answer the question about the feasibility of establishing a second generation of personal computers. In computers, PS / 2 isplzuyutsya 3.5-inch floppy disk in a hard outer skeleton, significantly reduces the possibility of data loss due to damage to the disk, which occurred in the application of 5.25-inch floppy disk used in a series of PC. New videostandarty sold in the PS / 2 provides a better quality display, and compatibility with the display, supported by the first generations of personal computers. Although the adapter card designed for a series of PC, may not be used to enhance computer connectors PS / 2, this seems a small fee for the opportunities provided by the architecture Mikrokanala, which requires the adapter boards have better grounding and more rigid construction of Compared with the adapter card, designed for computers IBM PC. Draft Mikrokanala allows the use of cards that contain independent microprocessors to work together with the chip on the motherboard PS / 2, as well as up to 15 additional processors that are supported on computers PS / 2 based Mikrokanala. Thus, Mikrokanalobespechivaet support of new technological developments. For computers PS / 2 based on the 80286 and 80386 microprocessors, the company IBM designed the new structure of the tire, which is called Mikrokanalom (Micro Channel). Architecture Mikrokanala requires a complete redesign of system expansion connector, which is currently incompatible with the sockets extension, in the computer PC. Because of this incompatibility, adapter card, which can be used in the computer model 25 and model 30, can not be applied in other models of PS / 2, and vice versa. Mikrokanal has several key advantages relative to the tire structure of PC. The first and, apparently, the most obvious to specialists familiar with older models of PC, this exception type switches DIP (Dual In-line Package bistatic placed in-line) on the adapter-governmental motherboards designed for installation in the connector expand Mikrokanala. Unlike the previous version, Mikrokanal provides automatic installation and configuration of all the extra set of computer circuit boards - a property company which IBM calls the program choice (Programmable Option Select - POS). Additional charges, designed for use with a PC, usually requires the user to position the DIP switches in a certain situation when you install this card, as well as the movement in the appropriate position switches DIP, located on the motherboard of your computer. Since the opportunities provided by the POS, providing automatic installation of the configuration of adapter cards designed for Mikrokanala when the power is turned on the computer, and if necessary reconfiguration of the software, we can say that POS simplifies the process of initializing the hardware and eliminates possible errors installing the setting of the DIP. A second possible advantage Mikrokanala compared with the PC bus is that Mikrokanal supports bus arbitration. This allows the processor installed on the expansion card, which in this case called zadatchikami (masters), to assume temporary management of the system. With the help of various schemes of arbitration devices to access the system data bus, if two or more devices are trying to get management Mikrokanalom at the same time, the algorithm implemented in hardware, allow this conflict. Using the hardware arbitration, the microprocessor is located on the motherboard, can transmit specific computational tasks adapter card designed specifically for this task. After the transfer of the main tasks of the microprocessor can perform other functions, which leads to increased productivity. Mikrokanal designed so that it can support only 16 of intelligent processors, including the microprocessor on the motherboard. This means that mikrokanal can support up to 15 additional processors, which perform independent functions such as communications, graphics, encryption, or intelligent drive management. Indeed, mikropotsessory placed on the adapter cards to be installed in the expansion connectors Mikrokanala may not be compatible with the chip on the motherboard. This is because the arbitration scheme to control access to the bus to transfer data between devices, providing flexibility in designing for manufacturers of the products. Another advantage Mikrokanala is possible to use the new board and new placement of the findings, which significantly reduces the computer generation of electromagnetic radiation (Electro Magnetic Interference - EMI). The new format of the adapter card is selected so as to correspond to the expansion connector Mikrokanala, and is optimized to provide high-density circuit design. This adapter allows you to pay Mikrokanala VLSI more than the fees, tire designed for PC. Placing the findings in the adapter board Mikrokanala such that every four output has ground output from both sides of the connector board. This placement of the findings shifted to two conclusions on the opposite sides of the connector, resulting in a signal related to the withdrawal becomes earth conclusion. All this allows to significantly reduce the EMI. PS/2: 25, 50Z, 55, 70 è Ð70.