3.2. System boards. Tires, interfaces

The main electronic part of the PC is structurally located in the system unit. A system unit can be of several sizes and types, for example, a desktop one, of the tower type. The various components of the computer inside the system unit are located on the motherboard, which is called the motherboard.

The motherboard plays a significant role, since the performance of a PC largely depends on its characteristics. There are several types of motherboards that are usually designed for specific microprocessors. The choice of the motherboard largely determines the possibilities of future computer upgrades. When choosing a motherboard, you must consider the following characteristics:

• • possible types of microprocessors used, taking into account their operating frequencies;
• • number and type of system bus connectors;
• • base fee;
• • the possibility of increasing operational and cache memory;
• • the ability to update the basic input-output system (BIOS).

On the motherboard are one or more integrated circuits. They control communications between the processor, memory, and I / O devices. They are called system chipsets .

Intel 440LX, Intel 440BX are in the greatest demand among microcircuits. The largest manufacturer of motherboards is Intel, which has introduced most of the technological and technical innovations for motherboards. However, Intel products are not cheap.

Directly on the motherboard is the system bus, which is designed to transfer information between the processor and the rest of the PC components. With the help of the bus, information is exchanged as well as the transmission of addresses and service signals.

IBM PC-compatible computers initially used a 16-bit bus operating at 8 MHz. After the appearance of new microprocessors and high-speed peripheral devices, a new standard was proposed - the ISA bus with a higher clock frequency. It contained the functions of arbitration, allowing to avoid conflict situations when several devices work together. This bus has increased throughput and achieved a large compactness, and the bus width of the ISA-16 and 32.

In 1989, an EISA tire was developed that actually became an ISA add-on. This tire was used mainly in high-performance servers and professional workstations with high performance requirements.

To increase system performance, from 1991 began to use the so-called local tires. They connected the processor directly to the peripheral controllers and thereby increased the overall speed of the PC. Among local buses, the VL-bus is the most famous, which was focused on PCs with microprocessors of the i486 family, although it can also work with Pentium processors.

Processor-independent PCI bus operates at 33 MHz and has a high data transfer rate. Especially for this bus, many peripheral adapters are released - video cards, disk controllers, network adapters, etc.

For work with graphic and video data developed the AGP bus, faster, than PCI. The AGP bus directly connects the graphics adapter to the PC's main memory, which is very important when working with video, two- and three-dimensional applications; it operates at 66 MHz.

Peripherals are connected to the system bus using controllers or adapters. Adapters are special boards that are different for different types of peripheral devices.