Open computer architecture

The company DEC in the early 70's. A computer with a new architecture was proposed. This open architecture of the computer allowed you to freely connect any peripheral devices, which provided free connection to the computer of any number of executive mechanisms. All this was achieved by connecting to a common information bus in accordance with the bus standard - a freely distributed document. This allowed firms to manufacture peripheral equipment to develop controllers for connecting to different standards buses.

Open architecture of the computer in the basis looks like this. The overall management of the entire system is performed by the central processor, which manages the common bus, allocating time to other devices to exchange information. The storage device stores executable programs and data and is coordinated by the levels of its signals with the signal levels of the bus itself. External devices whose signal levels differ from the bus signal levels are connected to it via a special controller. The controller matches the signals of the device with the bus signals and manages the device by commands coming from the central processor. The controller is connected to the bus by special devices - input/output ports. Each port has its own number, and the processor accesses to it, as well as to the memory cell, by this number. The processor has special control lines, the signal on which determines whether the processor is accessing the memory cell or the I/O port of the controller of the external device.

Open architecture of the computer, despite the advantages, has a serious drawback. When connecting to a common bus of devices with different speeds of exchange, "slow" delayed the work of "fast". Further increase in computer performance was found in the introduction of an additional local bus, to which "fast" devices were connected. In such an open architecture of the computer, the bus controller analyzes the port addresses transmitted by the processor and passes them to a controller connected to a common or local bus.

The controller of each device can be placed on a common board with a central processor or on a special board inserted into special connectors on a common card - expansion slots. With the development of microelectronics, functional nodes of the computer and controllers of standard devices began to be placed in a single chip. This made it possible to introduce two additional local buses for connecting the memory device and the display device, which have the largest amount of exchange with the central processor and with each other.

The open architecture of a modern computer includes, in addition, central and functional controllers. The central one plays the role of a switch that distributes information flows between the processor, memory, display device and other nodes of the computer.

The functional controller contains controllers for connecting the keyboard, mouse, printer, modem, etc.