The internal architecture of a personal computer

All the main components of a personal computer are inside the system unit: motherboard with CPU and RAM, hard drives and floppy disks, CD-ROM, etc. In addition, the system unit is the power supply. 

Motherboard. The main hardware component of computer is the motherboard. On the motherboard implements the backbone of information exchange, there are connectors to install the CPU and RAM, as well as slots for mounting controllers to external devices. 

The main part of the motherboard is the microprocessor (MP) or CPU (Central Processing Unit), he manages the operation of all PC components and software, describing algorithm of a solved task. MP has a complex structure in the form of electronic logic circuits.

As its component can be selected:

1.             ALU - an arithmetic logic unit, designed to perform arithmetic and logical operations on the data and memory addresses; 

2.             The microprocessor registers or memory — cache memory, working with the speed of the processor, ALU works with them; 

3.             OOH - the control device - management of all MP nodes, through generation and transmission to other components of the control pulses, coming from quartz oscillator, which you turn your PC starts to vibrate with constant frequency (100 MHz, 200-400 MHz). These fluctuations and set the pace for the entire motherboard; 

4.             JWP - interrupt system - special register, describing the state of MP, allows you to interrupt the MP at any time for immediate processing some incoming request, or putting it in the queue; after processing the request, the SPM provides recovery of interrupted process; 

5.             The control device via a shared bus interface system. 

To extend the capabilities of your PC and increase the functional characteristics of the microprocessor may additionally be supplied math coprocessor, serving to extend the set of commands MP. For example, a math co-processor IBM-compatible PC extends the capabilities of MP for floating-point calculations; the coprocessor in local networks (LAN processor) expands the functions of the MP in local networks. 

Characteristics of the processor:

- performance (performance, clock frequency) — the number of operations, performed per second. 

- bit depth — the maximum number of binary digits, over which can run at a time machine операция4. 

Memory - a device for storing data information and programs. The memory is divided first of all on internal (located on the motherboard) and external (available on a wide variety of external media). 

The internal memory is in turn divided into:

- ROM (permanent storage device) or ROM (read only memory), which contains - regular information, retained even while the power is off, which is used to test memory and PC hardware, bootstrap PC when you turn on. Entry on a special cassette of the ROM occurs at the factory of the manufacturer of the PC, and carries the traits of his personality. ROM size is relatively small - from 64 to 256 KB. 

- RAM (random access memory, OP — RAM) or RAM (random access memory), used for operational storage of programs and data, stored only for the duration of the PC. It is volatile, when the power is turned off information is lost. OP highlighted the special features and specifics of access: 

1.      OP stores not only data, but running the program;

2.      MP has direct access to OP, bypassing the system I/o.

Logical organization of memory addressing, the placement of data is determined BY, installed on the PC, namely OS. 

Installed RAM ranges from 64 KB to 64 MB and above, as a rule, OP has a modular structure and can be expanded by adding new circuits. 

Cache - has short access times, serves for temporary storage of intermediate results and the contents of the most frequently used registers and cells OP MP. 

The size of the cache memory depends on model of PC and is usually 256 KB.

External memory. Device external memory is very diverse. The proposed classification takes into account the media type, ie. a material object, able to store information. 

The tape drives have historically come before, than storage on magnetic disk. Reel-to-reel drives are used in supercomputers and mainframe. Tape drives are called streamers, they are designed to create backups of programs and documents, of value. The camera can record on regular VHS tape or on a special cassette. The capacity of the magazine to 1700 MB, belt length 120 m, width 3.81 mm (2 - 4 track). The speed of reading data-up to 100 KB/sec. 

Drives are storage media with direct access, ie. The PC can access the track, on which begins the section with the required information or where it is necessary to record new information, непосредственно5. 

Magnetic disks (MD)— as the storage medium being magnetic materials with special properties, allows you to capture two magnetization directions. Each of these States are associated with binary digits 0 and 1. Information on MD is written and read by magnetic heads along concentric circles - tracks. Each track is divided into sectors (1 sector = 512 b). The exchange between the disks and the OP happens a whole number of sectors. The cluster is the minimum allocation unit of data on the disk, it may contain one or more contiguous sectors of the track. When writing and reading CBMs rotates on its axis, while the mechanism control of the magnetic head brings it to the selected read or write track. 

Data on disks are stored in files named areas of external memory, allocated to store array data. Clusters, allocated to the file, can be in any free space on the disk space and not necessarily adjacent. All information about, where recorded pieces of the file, is stored in the file allocation table FAT (file allocation table). For packages MD (it drives, installed on one axis) and for double-sided disc introduces the concept of the cylinder - the set of tracks of the MD, located at the same distance from the center. 

On the GMI magnetic layer is applied on a flexible basis. The diameter of the KMT: 5,25″ and 3.5″. The capacity of the KMT from 180 KB to 2,88 MB. The number of tracks on one surface - 80. The speed of rotation from 3000 to 7200 rpm. Average access time 65 - 100 MS. 

Each new diskette before work must be formatted, ie. created the structure of recording information on its surface: the layout of the tracks, sectors, recording markers, FAT table. Diskettes should be stored carefully, keep away from dust, mechanical damage, magnetic fields, solvents. This is the main disadvantage of this type of drives.

 

HDD or "hard drive" made of aluminum alloys or of ceramic and coated with ferrocom, together with the block of magnetic heads placed in a hermetically sealed enclosure. The capacity of the drives due to the extremely dense recording up to several gigabytes, the performance is also higher, than removable disks (by increasing the speed of rotation, unnecessarily. the disc is rigidly fixed on the axis of rotation). The first model appeared on the IBM at 1973 g. She had the capacity 16 KB and 30 tracks/30 sectors, that coincided with the popular caliber guns 30’730″ the Winchester. 

Diameter GMD: 3,5″ (there is a 1.8″ 5.25″). The speed of rotation 7200 rpm, the access time is 6 MS. 

Each GMD is in the process of low-level format on the medium is recorded service information, which defines the markup cylinders of the disk into sectors and enumerates them, bad sectors are marked to exclude them from the operation of the disk. In PC there is one or two storage drives. One train can be broken with the help of special programs on multiple drives and work with them as with different railway. 

Hardware RAID - apply to the machines, database servers, and supercomputers, they represent a matrix with redundant independent disks, several HDD combined into one logical drive. You can combine up to 48 the physical disks of any capacity, forming up to 120 logical drives (RAID7). The capacity of such discs is to 5Т6 (terabyte=1012). 

NOD (the optical drive) share on:

- not writable laser-optical disks or CD-ROMs (CD-ROM). Supplied by the manufacturer with the already stored information. The entry on them is possible in laboratory conditions with a laser beam of large power. In the optical disc drive of your PC, this track is read by a laser beam of less power. Because of the extremely dense burn CD-ROMs have the capacity to 1,5 GB, access time from 30 to 300 MS, the read speed from 150 to 1500 KB/sec; 

- rewritable CD-ROMs have the ability to record information directly from the PC, but this requires a special device. 

Magneto-optical disks (ZIP) recording on such a disc is produced under the high temperature magnetization of the active layer, and read by a laser beam. These discs are convenient to store information, but the equipment is expensive. The capacity of such a disk drive to 20,8 MB, access time from 15 to 150 MS, the speed of reading data to 2000 KB/sec. 

Controllers are to ensure direct communication with the OP, bypassing MP, they are used for devices fast data exchange with the OP - Floppy disk drive, DB AG, display, etc., ensure the work group or network mode. Keyboard, display, mouse are slow devices, therefore, they are connected to the motherboard controllers and are OP in their designated memory areas.

 

Ports are input and output, universal (enter - conclusion), they serve to provide information exchange with an external PC, not very fast devices. Information, entering through the port, goes to MP, and then in the OP. There are two types of ports:

- consistent — provides a bit-exchange of information, usually to a port connected modem; 

- parallel — provides byte information exchange, to a port connecting the printer. Modern PCs are usually equipped 1 parallel and 2 serial ports. 

Video monitor device, designed to display information from the PC to the user. The monitors are monochrome (green or amber picture, large resolution) and color. Best quality RGB monitors, have high resolution graphics and colors. Using the same principle of electronic beam tube like a TV. In portable PCs use electroluminescent or liquid crystal panels. Monitors can work in text and graphic modes. In text mode the image is composed of characters — special characters, stored in the video memory of the display, and in the graphic image consists of pixels of a particular brightness and color. Key features of video monitors - resolution (from 600х350 up to 1024x768 pixels), the number of colors (for color) -from 16 to 256, the framerate is fixed 60 Hz.