Topic: PC Devices.
Educational questions:
1. Devices that make up the PC architecture.
2. Internal devices of the PC.
3. External devices PC.
Modern computers are very diverse both in their design and in the functions they perform.
If we consider computers by their functionality, we can conditionally classify them:
1. "Household" computers (PC);
2. "Educational" computers (simplified architecture);
3. "Professional" computers (workstations in production, office, etc.);
4. Computer servers (management of workstations united in networks, storage of large amounts of information, etc.), etc.
Depending on the functions performed and, thanks to the open architecture, the computer device is very diverse. As a result of scientific and technological development, the computer architecture is constantly being improved (evolving).
Open architecture of modern PCs:
| Interface system |
Computer architecture is the most general design principles that implement programmatic control of the interaction of its main units. Computer architecture is, first of all, blocks and devices, as well as the structure of connections between them.
The blocks and devices that make up the PC architecture are also divided into two groups:
· internal devices;
· external (peripheral) devices.
Internal devices probably received such a general name, since they are combined at one housingcalled system unit PC .
The appearance and dimensions of the case of system units are varied. However, a mandatory element for all enclosures is connectors for connecting external devices and control interface.
With a huge variety of options made up of devices, systems placed in the case of the system unit, it is imperative minimum them picking.
"Required" include:
· Power Supply... On average, their power is 100 - 400 watts. The more devices in the system, the more power the power supply should have. (Average power 200 - 300 W).
· System (motherboard) board... This multifunctional device is central to open architecture computers. In terms of physical structure, it is a very complex multilayer printed circuit board.
In terms of functionality, the motherboard performs a set of functions for integrating devices and ensuring their interaction.
As the elements of the configuration of the computer architecture are standardized, the tendency is to include them in the composition of the motherboard.
The first motherboard was developed by IBM in August 1981 (PC-1). From the very beginning, the motherboard was conceived as a component that provides a mechanical connection and electrical connection between all other hardware. In addition to these functions, it also supplies electricity (power) to the computer components.
Modern motherboard architecture (generalized).
The modern MP contains a large number of controllers (specialized microprocessors) that ensure the interaction of all devices. They are implemented in two sets of microcircuits, historically called "northbridge" and "southbridge" or chipsets.
· Memory controller hub, or "north bridge" (English North Bridge) provides the processor, RAM and video subsystem;
· I / O controller hub, or "South Bridge" (English South Bridge) provides work with external devices.
Bus bandwidth.
The speed of the processor, RAM and peripheral devices varies significantly.
The performance of the device depends on:
· Clock frequency of data processing (usually measured in megahertz - MHz);
· And bit width, i.e. the number of data bits processed per clock cycle (the time interval between the supply of electrical impulses that synchronize the operation of PC devices).
Accordingly, the data transfer rate - the bandwidth of the buses connecting these devices must also differ. The bus bandwidth is equal to the bus width (bits) multiplied by the bus frequency (Hz - hertz. 1Hz \u003d 1 cycle per second).
System bus (FSB stands for Front Side Bus) transfers data between the North Bridge and the microprocessor. In modern PCs, the system bus is 64 bits wide and has a frequency of 400 MHz to 1600 MHz.
The bandwidth can reach 12.5 GB / s.
Memory bus transfers data between the "North Bridge" and PC RAM. Has the same performance as the system bus.
PCI Express bus (Peripherial Component Interconnect Bus Express - accelerated bus of interaction of peripheral devices) transfers data between the North Bridge and the video card (video card). The bandwidth of this bus can reach 32 GB / s.
SATA bus (English Serial Advanced Technology Attachment) transfers data between the South Bridge and an external memory device (hard disks, CD and DVD drives, floppy disks). The throughput can be as high as 300 MB / s.
USB bus (English Universal Serial Bus - universal serial bus) transfers data between the South Bridge and various external devices (scanners, digital cameras, etc.). Bandwidth up to 60 MB / s. Provides connection to a PC simultaneously up to 127 peripheral devices.
Other important functions of the motherboard - providing a mechanical connection and electrical connection between all other hardware, as well as supplying power to them.
There is a wide variety of motherboard designs.
One of the characteristics of the motherboard is the form factor (AT / ATX). It determines the size of the motherboard and the locations of the hardware components on it.
Simplified layout of the joint venture components.
The central unit of the PC is considered to be an electronic unit located in a special connector on the motherboard, called cPUor microprocessor.
Initially, the microprocessor combined an arithmetic-logic device ( ALU) and control devices ( Uu).
The commands executed by the microprocessor usually involve arithmetic operations, logical operations, transfer of control, and movement of data between registers, RAM and I / O ports. The microprocessor communicates with external devices thanks to its address, data and control buses, which are brought out to special contacts of the microcircuit case.
The control unit generates control signals that are sent through the instruction buses to all computer blocks.
Simplified control scheme
Command register - a storage register that stores the instruction code: the code of the operation to be performed and the addresses of the operands involved in the operation.
Firmware read-only memory - stores in its cells the control signals (impulses) necessary for performing information processing operations in the PC units. The operations decoder, reading the operation code from the command recorder, selects the required sequence of control signals in the firmware ROM - the command code.
Address generation node - a device that calculates the full address of a memory cell (register) using the details coming from the command register.
Code buses of data, addresses and instructions - parts of the internal microprocessor bus that transfer signals between the processor and other PC devices.
In general UU generates control signals to perform the following basic procedures:
· Selections from the register - the counter of the RAM cell address where the next program command is stored;
Fetching from RAM cells when the next command and receiving the read command into the command register;
· Decoding of the operation code and signs of the selected command;
Reading from the corresponding to the decoded code of operations of the ROM cells of the firmware of the control signals (impulses), which determine in all the computer blocks the procedure for performing the given operation, and sending the control signals to these blocks;
· Reading from the command register and the MPP register (microprocessor memory) of the individual constituent addresses of the operands;
· Selection of operands and execution of the specified operation of their processing;
· Recording results in memory;
· Formation of the address of the next program command.
Arithmetic logic unit is intended for performing arithmetic and logical operations of information transformation.
Hello dear readers of the blog site. Very often on the Internet you can find a lot of any computer terminology, in particular - such a concept as "System bus". But few people know what exactly this computer term means. I think today's article will help clarify.
The system bus (backbone) includes a data, address and control bus. Each of them transmits its own information: data bus - data, addresses - respectively, address (devices and memory cells), control - control signals for devices. But now we will not delve into the jungle of the theory of organization of computer architecture, we will leave it to university students. Physically, the trunk is represented as (contacts) on the motherboard.
It is no coincidence that I pointed to the inscription "FSB" in the photo for this article. The point is that for processor chipset connection it is the FSB bus that is responsible, which stands for "Front-side bus" - that is, "front" or "system". And, which is usually guided by when overclocking a processor, for example.
There are several types of FSB, for example, on motherboards with Intel processors, the FSB is usually a type of QPB, in which data is transferred 4 times per clock. If we are talking about AMD processors, then data there is transmitted 2 times per cycle, and the bus type is called EV6. And in the latest CPU models from AMD, there is no FSB at all, its role is played by the latest HyperTransport.
So, data is transferred between and the central processor at a frequency that is 4 times higher than the FSB frequency. Why only 4 times, see the paragraph above. It turns out that if the box says 1600 MHz (effective frequency), in reality the frequency will be 400 MHz (actual). Later, when it comes to overclocking the processor (in the following articles), you will learn why you need to pay attention to this parameter. For now, just remember, the higher the frequency, the better.
By the way, the inscription "O.C." means literally "overclocking", this is short for English. Overclock, that is, this is the maximum possible frequency of the system bus that the motherboard supports. The system bus can easily operate at a frequency significantly lower than that indicated on the package, but not higher than it.
The second parameter that characterizes the system bus is. This is the amount of information (data) that it can pass through itself in one second. It is measured in Bits / s. The bandwidth can be independently calculated using a very simple formula: bus frequency (FSB) * bus width. You already know about the first factor, the second factor corresponds to the processor capacity - remember, x64, x86 (32)? All modern processors are already 64-bit.
So, we substitute our data into the formula, in the end we get: 1600 * 64 \u003d 102 400 MB / s \u003d 100 GB / s \u003d 12.5 GB / s. This is the bandwidth of the trunk between the chipset and the processor, or rather, between the north bridge and the processor. I.e system bus, FSB, processor bus are all synonyms... All connectors of the motherboard - video card, hard disk, RAM, "communicate" with each other only through the trunk. But FSB is not the only one on the motherboard, although it is certainly the most important.
As you can see from the figure, the Front-side bus (the thickest line) actually connects only the processor and the chipset, and already from the chipset there are several different buses in other directions: PCI, video adapter, RAM, USB. And it is not at all a fact that the operating frequencies of these sub-buses should be equal or multiples of the FSB frequency, no, they can be completely different. However, in modern processors, the RAM controller is often moved from the north bridge to the processor itself, in which case it turns out that a separate RAM line does not seem to exist, all data between the processor and the RAM is transmitted via the FSB directly with a frequency equal to the FSB frequency.
That's all for now, thanks.
It is not at all necessary for an ordinary user to know the structure of a computer. But if you want to consider yourself an advanced user who can easily cope with any set computer task, and besides, is going to independently assemble your first system unit in the near future, then such knowledge is simply necessary.
The functioning of a computer is impossible without the presence of at least one of the following systems:
- Processor.
- Video cards.
- Random access memory.
But even all these components together will not be able to function. For this, it is necessary to organize a connection between them, through which logical and computational operations would be carried out. Such communication systems organize the system buses of the computer. Therefore, we can say that this is another indispensable component of the system unit.
System bus
The system bus is a collection of data transmission paths that provide interconnected operation between the rest of the computer: processor, video adapter, hard drives and other components. This device consists of several levels:
- mechanical;
- electrical or physical;
- logical and control level.
Primary division of system buses
The division of tires is based on several factors. The leading indicator is the location. According to this indicator, tires are:
- Internal, which provide the interconnection of the internal components of the system unit, such as the processor, RAM, motherboard. Such a system bus is also called local, as it serves to communicate with local devices.
- External, which are used to connect external devices (adapters, flash drives) to the motherboard.
In the most general case, a system bus can be any device that serves to combine several devices into one system. Even network connections, such as the Internet, are in some way a system bus.
The most important communication system
All the activities that we carry out through a computer - creating various documents, playing music, running computer games - would be impossible without a processor. In turn, the microprocessor would not be able to do its job if it did not have communication channels with other important elements, such as RAM, ROM, timers and I / O connectors. It is for this function that the computer has a system bus of the processor.
Computer speed
For the functioning of the microprocessor, the system of communication channels includes several buses at once. These are tires:
The number of presented types of system communication channels of the processor can be from one or more. Moreover, it is believed that the more tires are installed, the greater the overall performance of the computer.
An important metric that also affects PC performance is the system bus bandwidth. It determines the speed of information transfer between local systems of an electronic computer. It is quite simple to calculate it. It is only necessary to find the product between the clock frequency and the amount of information, that is, the byte that is transmitted in one clock cycle. So, for the long-obsolete ISA bus, the throughput will be 16 MB / s, for the modern PCI Express bus, this value will be around 533 MB / s.
Types of computer buses
The history of computer technology goes back more than one decade. Together with the development of new components, new types of system buses were also developed. The very first such communication channel was the ISA system. This component of the computer provides data transfer at a rather slow speed, but it is sufficient for the simultaneous operation of the keyboard, monitor and some other components.
Despite the fact that it was invented more than half a century ago, this system bus has been actively used today, confidently competing with more modern representatives. This was possible thanks to the release of a large number of extensions that increased its functionality. It is only in recent years that processors have begun to be released without ISA.
Modern system buses
The VESA bus has become a new word in the field of computer technology. Designed specifically for direct connection of external devices to the processor itself, it still has high data transfer rates and provides high processor performance.
But such a system of communication channels is not able to ensure the proper functioning of the microprocessor. Therefore, it is implemented in the system together with ISA and acts as another extension.
That's all the quick reference that should shed light on one of the most important components of modern computers. It should be said that only the smallest piece of information about computer buses is presented here. Their full study has been carried out in special institutions for several years. Such detailed information is necessary directly for the development of new models of microprocessors or for the modernization of existing ones. PCI bus is the closest competitor to the previous representative of data transmission channels. This system bus was developed by Intel specifically for the production of its own brand processors. This device is capable of providing an even higher data transfer rate and does not need additional elements, as in the previous example.
11 System bus, system bus modes, programmable system devices
Buses are sets of conductors through which signals are exchanged between the internal devices of the computer;
System bus - designed to transfer information between the processor and the rest of the electronic components of the computer. The system bus is used to address devices and exchange special service signals. Simplistically, the system bus can be represented as a set of signal lines, united by their purpose (data, addresses, control). The system bus is a set of electrical signal conductors and a system of protocols for connecting devices using these conductors. The type and characteristics of the protocols for transferring information on the system bus determine the speed of information transfer between individual devices on the motherboard. The system buses of personal computers are standardized both in terms of the number of contacts and bit depth (the number of conductors used for simultaneous data transmission), and the protocols of communication between devices through conductors. The system bus connects all computer devices into a single whole and ensures their interaction, mutual control and work with the central processor. In personal computers, system buses of ISA, EISA, VLB and PSI standards are used. Nowadays, they now use only the PCI bus, of course you can still find ISA, but it is too slow in comparison with PCI, so I no longer release it.
18 Computer video system. Work principles. Areas of use
Video card (video adapter) Together with the monitor, the video card forms the video subsystem of a personal computer. A graphics card hasn't always been a component of a PC. At the dawn of the development of personal computing in the common area of \u200b\u200brandom access memory, there was a small dedicated screen memory area, into which the processor entered data about the image. A special screen controller read data on the brightness of individual screen points from the memory cells of this area and, in accordance with them, controlled the sweep of the horizontal beam of the monitor's electron gun. With the transition from black and white monitors to color monitors and with an increase in screen resolution (the number of vertical and horizontal dots), the video memory area became insufficient to store graphic data, and the processor ceased to cope with the construction and updating of the image. Then all the operations related to screen control were separated into a separate block called the video adapter. Physically, the video adapter is made in the form of a separate daughter board, which is inserted into one of the slots of the motherboard and is called a video card. The video adapter took over the functions of a video controller, video processor and video memory. During the existence of personal computers, several video adapter standards have changed: МDA (monochrome); CGA (4 colors); EGA (16 colors); VGA (256 colors). Currently, SVGA video adapters are used, which provide optional reproduction of up to 16.7 million colors with the ability to randomly select the screen resolution from a standard range of values \u200b\u200b(640x480, 800x600,1024x768, 1152x864; 1280x1024 pixels and so on). Screen resolution is one of the most important parameters of the video subsystem. The higher it is, the more information can be displayed on the screen, but the smaller is the size of each individual point and, thus, the smaller is the apparent size of picture elements. Using a higher resolution on a small monitor leads to the fact that image elements become illegible and working with documents and programs causes eye fatigue. Using a lower resolution leads to the fact that image elements become large, but they are very small on the screen. If the program has a complex control system and a large number of screen elements, they do not completely fit on the screen. This leads to a decrease in labor productivity and inefficient work. Color resolution (color depth) determines the number of different hues that a single point on the screen can take. The maximum possible color resolution depends on the properties of the video adapter and, first of all, on the amount of video memory installed on it. In addition, it depends on the set screen resolution. At high screen resolutions, less video memory has to be allocated per pixel, so color information is forced to be more limited. The minimum requirement for color depth today is 256 colors, although most programs require at least 65 thousand colors (High Colo mode). The most comfortable work is achieved with a color depth of 16.7 million colors (sharp True Color). Working in True Color full color at high screen resolutions requires significant video memory. Modern video adapters can also perform image processing functions, reducing the load on the central processor at the cost of additional video memory. Until recently, video adapters with a memory capacity of 2-4 MB were considered typical, but today 16 MB is considered common. Video acceleration is one of the properties of the video adapter, which lies in the fact that some of the operations for building images can occur without performing mathematical calculations in the main processor of the computer, but purely by hardware means converting data in the video accelerator microcircuits. Video accelerators can be part of the video adapter (in such cases, they say that the video card has hardware acceleration functions), but they can be supplied as a separate board installed on the motherboard and connected to the video adapter. There are two types of video accelerators - flat (2D) and three-dimensional (3D) graphics accelerators. The former are most effective for working with application programs (usually office use) and are optimized for the Windows operating system, while the latter are focused on the operation of multimedia entertainment programs, primarily computer games and professional 3D graphics processing programs. Usually, in these cases, different mathematical principles are used to automate graphic operations, but there are accelerators that have functions of both two-dimensional and three-dimensional acceleration.
An integral part (although for the first time the display was implemented on some second-generation computers, for example, on "MIR-2" - a very interesting domestic development in many respects). Figure 3.1 - Computer bus architecture To obtain a stable picture on the monitor screen, it must be stored somewhere. That's what video memory is for. First, the contents of the video memory are generated by the computer, and ...
User. With the help of the keyboard, they control the computer system, and with the help of the monitor, they receive a hail from it. Operating principle. The keyboard belongs to the standard means of a personal computer. Its main functions do not need to be supported by special system programs (drivers). The necessary software to start working with a computer is already available in the ROM chip in ...
The main component of every PC is the motherboard (system board). It contains all its main elements - a processor, RAM, video card, controllers, as well as slots and connectors for connecting external peripherals. All components of the motherboard are interconnected by a system of conductors (lines) through which information is exchanged. This collection of lines is called a data bus. A bus connecting only two devices is called port ... As an example, consider the structure of, for example, such a PC bus:
The interaction between PC components and devices connected to different buses is carried out using the so-called bridges, implemented on one of the Chipset microcircuits.
The buses in the PC differ in their functional purpose:
- system bus used by Chipset chips to send information to and from the processor;
- cache bus intended for information exchange between the processor and external cache memory;
- memory bus used to exchange information between RAM and processor;
- i / O buses are used to exchange information with peripheral devices.
I / O buses are divided into local and standard. Local an I / O bus is a high-speed bus designed to exchange information between high-speed peripheral devices (video adapters, network cards, etc.) and a processor. Currently, the PCI Express bus is used as the local bus (in the past, the AGP bus was used - Accelerated Graphics Port).
Standard the I / O bus is used to connect slower devices (eg mice, keyboards, modems). Until recently, this bus was the ISA bus. Currently, the USB bus is widely used.
Bus components
Any bus architecture has the following components:
- data lines (data bus). The data bus provides data exchange between the processor, expansion cards installed in slots and memory. The higher the bus width, the more data can be transferred per clock cycle and the higher the PC performance. Pentium-based computers have a 64-bit data bus.
- lines for addressing data (address bus). The address bus is used to indicate the address of a device with which the processor exchanges data. Each PC component, each I / O port and RAM cell has its own address.
- data control lines (control bus). A number of service signals are transmitted over the control bus: write / read, readiness to receive / transmit data, confirm data reception, hardware interrupt, control, and others. All control bus signals are intended for data transmission.
- bus controller, controls the process of data exchange and service signals and is usually performed as a separate microcircuit, or in the form of a compatible chipset - Chipset.
Main characteristics of the tire
Bus width is determined by the number of parallel conductors included in it. The first ISA bus for the IBM PC was 8-bit, i.e. it was possible to transmit 8 bits simultaneously. System buses for modern PCs, for example, Pentium IV - 64 - bit.
Bus bandwidth is determined by the number of bytes of information transmitted over the bus per second. To determine the bus bandwidth, multiply the bus clock frequency by its bit width. For example, if the bus width is 64 and the clock frequency is 66 MHz, then throughput \u003d 8 (bytes) * 66 MHz \u003d 528 MB / sec.
Bus frequency is the clock frequency at which data is exchanged over the bus.
External devices are connected to buses via an interface.
PC bus standards
The principle of IBM compatibility implies the standardization of the interfaces of individual PC components, which, in turn, determines the flexibility of the system as a whole, i.e. the ability to change the system configuration as needed and connect various peripheral devices. In case of incompatibility of interfaces, controllers are used.
System bus (FSB - Front Side Bus) is a bus designed to exchange information between the processor, memory and other devices included in the system. System buses include GTL , having a capacity of 64 bits, a clock frequency of 66, 100 and 133 MHz; EV6 , whose specification allows to increase its clock frequency to 377 MHz.
I / O buses are improved in accordance with the development of PC peripherals.
- ISA bus was considered a PC standard for many years, however, it is still retained in some PCs along with the modern PCI bus. Intel has partnered with Microsoft to develop a phase-out strategy for the ISA bus. Initially, it is planned to exclude ISA connectors on the motherboard, and later to exclude ISA slots and connect floppy drives, mice, keyboards, scanners to the USB bus, and hard drives, CD-ROM drives, DVD-ROM drives to the IEEE 1394 bus.
- EISA bus was a further development of the ISA bus in the direction of improving system performance and compatibility of its components. The bus was not widely used due to its high cost and bandwidth, which was inferior to the bandwidth of the VESA bus that appeared on the market.
- VESA bus or VLB , is designed to connect the processor with fast peripherals and is an extension of the ISA bus for exchanging video data. In the days when the CPU 80486 processor dominated the computer market, the VLB bus was quite popular, but now it has been supplanted by the more efficient PCI bus.
- PCI bus Peripheral Component Interconnect bus (Peripheral Component Interconnect bus) was developed by Intel for the Pentium processor. The underlying principle behind the PCI bus is the use of so-called bridges, which communicate between the PCI bus and other types of buses. The PCI bus implements the Bus Mastering principle, which implies the ability of an external device to control the bus when sending data (without the participation of the processor). During the transfer of information, the device supporting Bus Mastering seizes the bus and becomes the master. In this case, the CPU is freed up for other tasks while data transfer is taking place. In modern motherboards, the PCI bus clock speed is set to half the system bus clock speed, i.e. at 66 MHz FSB, the PCI bus will operate at 33 MHz. The PCI bus has now become the de facto standard among I / O buses.
- AGP bus - a high-speed local I / O bus designed exclusively for the needs of the video system. It links the video adapter to the PC's system memory. The AGP bus was developed from the PCI bus architecture, so it is also 32-bit. However, at the same time it has additional opportunities to increase the throughput, in particular, through the use of higher clock frequencies. If the standard 32-bit PCI bus has a clock frequency of 33 MHz, which provides a theoretical PCI bandwidth of 33 x 32 \u003d 1056 Mbit / s \u003d 132 MB / s, then the AGP bus is clocked by a signal with a frequency of 66 MHz, so its bandwidth is mode 1x is, 66 x 32 \u003d 264 MB / s; in 2x mode, the equivalent clock frequency is 132 MHz, and the bandwidth is 528 MB / s; in 4x mode the throughput is about 1 GB / sec.
- PCI Express - In 2004, Intel developed a PCI-Express serial bus with a bandwidth of about 4 Gb / s. Each device connected to this bus is assigned its own channel with a speed rate of 250 Mb / s. In this case, you can use several channels at once, for example, when transferring data to a video card. Also, the pluses of this bus include "hot swapping" of any device connected to it, even without turning off the power of the system unit. The high peak performance of the PCI Express bus allows it to be used instead of AGP and PCI buses; PCI Express is expected to replace these buses in personal computers.
- USB bus (Universal Serial Bus) was designed to connect medium-speed and low-speed peripherals. For example, the speed of information exchange via the USB 2.0 bus is 45 MB / s - 60 MB / s. To computers equipped with a USB bus, you can connect peripheral devices such as a keyboard, mouse, joystick, printer without turning off the power. The USB bus supports Plug & Play technology. When a peripheral is connected, it is automatically configured.
- SCSI bus (Small Computer System Interface) provides a data transfer rate of up to 320 MB / s and provides for connecting up to eight devices to one adapter: hard drives, CD-ROM drives, scanners, photo and video cameras. There is a wide range of SCSI versions, from the first SCSI I, which has a maximum throughput of 5 MB / s, to the Ultra 320, which has a maximum bandwidth of 320 MB / s.
- UDMA bus (Ultra Direct Memory Access - Direct Memory Connection). UDMA transfers data from the hard drive at speeds up to 33.3 MB / s in mode 2 and 66.7 MB / s in mode 4.
- IEEE 1394 bus is a high-speed local serial bus standard developed by Apple and Texas Instruments. The IEEE 1394 bus is designed to exchange digital information between PCs and other electronic devices, especially for connecting hard drives and audio and video information processing devices, as well as for running multimedia applications. It is capable of transmitting data at speeds up to 1600 Mbps, working simultaneously with several devices that transmit data at different speeds, like SCSI. Like USB, the IEEE 1394 bus fully supports Plug & Play technology, including the ability to install components without disconnecting the PC's power. Almost any device capable of working with SCSI can be connected to a computer via the IEEE 1394 interface. These include all kinds of disk drives, including hard drives, optical drives, CD-ROMs, DVDs, digital camcorders, tape recorders, and many other peripherals. Thanks to such wide possibilities, this bus has become the most promising for combining computers with consumer electronics.
Serial and parallel ports
Input and output devices such as a keyboard, mouse, monitor, and printer are standard on the PC. All peripheral input devices must be connected to the PC in such a way that the data entered by the user can not only enter the computer correctly, but also be efficiently processed in the future. For data exchange and communication between the peripherals (input / output devices) and the data processing module (motherboard), parallel or serial data transmission can be organized.
Parallel port. A PC usually has 2 parallel ports: LPT1 and LPT2 ... You can connect printers and scanners to them. Currently, LPT ports are rarely used, modern printers and scanners are mainly connected to universal USB ports.
Serial ports. A PC usually has 4 serial ports: COM1 – COM4 ... These are legacy ports and are rarely used in modern PCs. You can connect to them: a mouse of the old design (with a mechanical ball) and some other slow devices.
PS / 2 - a port for connecting a keyboard and mouse, which at one time became widespread and is still available in many modern computers.
Universal USB port . USB ports connect a variety of devices, from printers and scanners to flash drives and external drives, as well as camcorders and webcams, cameras, phones, music players, and more.
PC Slots
In order for the motherboard to be able to communicate with other, separately plug-in cards, special sockets are used, which are called slots.
PCI slots... PCI is a standard not only for the slot, but also for the bus itself (the channel through which information is transmitted between computer devices). For a long time, PCI slots have been used to connect external devices (sound card, network card, and other controllers). There are three or four PCI slots on modern motherboards. It is very easy to find them - they are the shortest and usually white, separated by a jumper into two unequal parts. Today PCI slots are combined with new PCI-Express slots (used to connect video cards).
PCI Express slots. PCI-Express has two types of slots for connecting additional cards:
Short PCI-Express x1 (data transfer rate - 250 Mb / s)
Long PCI-Express x16 (up to 4 Gb / s) - for connecting a video card.
Slots for installing RAM - they are easy to distinguish among all connectors, they are equipped with special latches. There can be from two to four of them on the board, which allows installing from 512 MB to 4 GB of RAM. Slots are rigidly tied to the type of RAM, i.e. DDR2 memory slot cannot accommodate DDR3 memory. Sometimes on the same motherboard there are several slots for different types of memory.
