MOTHERBOARD

Introduction.

The most important part and backbone of a computer is the motherboard. It is where the processor, RAM, BIOS, chipset, auxiliary circuits, etc. are located. The motherboard is largely determined by the performance and functionality of the computer, including the possibility of upgrades. The high performance of the motherboards, and ultimately the entire computer system, is achieved through their continuous improvement based on the use of the latest computer technologies.

Traditionally, the central element that defines a computer’s computing capabilities is the processor, which is connected to the motherboard via a suitable connector. The most widespread sockets are of the following types: for Pentium, Pentium MMH and other similar processors – Socket 7, for Celeron, Pentium II, Pentium III, depending on their models – Slot 1 or Socket 370, for Pentium II Xeon, Pentium III Xeon – Slot 2, for AMD Athlon, AMD Duron, AMD ThunderBird processors – Slot A or Socket A. At the same time, with the increase of share of processors, connected through Socket type connectors, the production of corresponding motherboards increases. Technology continuity and modernization of computers created on the basis of motherboards with Slot 1/Slot A connectors, is provided by using of corresponding Socket processors with special adapter boards.

MAIN BOARD FEATURES

1. Supported processors. Each processor is characterized by a certain set of parameters. The most important are clock frequencies – internal and external, supply voltages – one or more, voltage values, etc. Processors have certain design differences closely connected with the peculiarities of their internal structure. Usually the following information is sufficient to identify a processor: manufacturer; processor type, e.g. Pentium, Pentium II/III, AMD Athlon, etc.; socket (Socket 7, Slot 1, Socket 370, etc.); external and internal frequencies.

2. Chipset. A wide variety of chipsets are being used on motherboards today, which affect both the performance of the motherboard and its functionality, as well as the cost of the board, and ultimately, the price of the computer. The chipset, or chipset, on which the motherboard is built. The chipset is the largest (after the processor) chipset in the computer, and the largest of the chipsets soldered to the motherboard. What function does the chipset perform? The chipset provides the connection between the main components on the motherboard, primarily the processor and memory. Therefore, of course, the chipset also affects the performance of the computer as a whole, because if, for example, the chipset is slow in working with memory, then the system works slower than a system with the same processor and memory, but another, faster working with memory chipset. But the function of linking all components into a single system is not the only function of the chipset. In addition, a modern chipset contains a number of basic, basic controllers for the various devices connected to the motherboard.

Disk drive controller (it’s called FDC – Floppy Disk Controller and FDD – Floppy Disk Drive), you can connect 2 disk drives to it;

Hard disk controller (the controller is commonly called IDE Controller and the hard disk – HDD – Hard Disk Drive), and the controller built into the chipset supports two ports to connect hard disks and to each port can be connected to two disks, i.e. a standard motherboard can connect up to 4 hard disks.

Printer port controller (also called parallel port or LPT port). As its name suggests, you connect your printer to this port, and often a scanner is also connected to it.

Communication ports (2 pcs.), they also talk about serial ports, COM – ports. To these ports can connect a mouse, modem (a device for communication with other computers via telephone lines), some exotic printers (usually from mobile computers), etc.

A keyboard controller and a special mouse port controller. This kind of connector is commonly referred to as a PS/2. Therefore, they talk about the PS/2 mouse and keyboard port.

Universal Serial Bus (USB) controller. This is quite a new bus and it is interesting because it allows to connect 127 serial devices to one port! That said, the current implementation of USB in chipsets offers very slow speeds, but a new version of the USB bus has been developed and should probably be available in chipsets by 2001. Typically, a chipset consists of several chips, most often of two. These chipsets are commonly referred to as bridges. One chip provides the connection of the motherboard components, it is usually called the North bridge, the other chip is called the South bridge, it is primarily responsible for the controllers integrated into the chipset. There are also other names for chipsets (Hub, but more on that later). There are chipsets, consisting also of 1, 3, 4 chips. From the chipset, based on which the motherboard is built, depend on all the features that the board provides. In particular, the type of processor used, the type and amount of RAM depend primarily on the chipset. So, clearly, the chipset is sort of the heart of the motherboard, and certainly its most important component.

3. System Bus and Frequency Parameters. It’s possible to set the necessary processor clock frequencies with the existing jumpers on the board or using BIOS features: external – for the processor and its bus (FSB), internal – for the processor and L1, L2 cache memory. For example, some boards support 50, 60, 66 MHz, some support 66, 100 MHz, some support 100, 133 MHz. And some allow you to set not only the standard frequency – it’s usually 60, 66, 100, 133 MHz, corresponding to the recommended modes, but also additional frequencies, allowing you to set the forced modes (overclocking).

4. External cache memory size and type (L2) for Socket 7 processors. As you know, the total PC performance depends on the size and type of cache memory. Most motherboards have a 512 Kbyte cache size that can be expanded to 1 Mbyte or even 2 Mbytes.

5. The amount, type and number of RAM slots. Most of modern motherboards allow you to install memory up to at least 256 Mbytes DIMM SDRAM, and some allow up to 1 Gbyte or even 1.5 Gbytes.

6.Controllers and adapters. Modern motherboards already include hard and floppy disk controllers, and some of the boards also include audio and video adapters. On the one hand, it provides compactness of the PC and complete absence of any conflicts between the devices. On the other hand, it is more difficult to make upgrades.

7.The number and types of slots (AGP, PCI, ISA, AMR) for controller cards. Defines the number and standard (AGP, PCI, ISA, AMR) of controllers that can be installed in the slots of the motherboard. This determines the functionality of the PC. The required number and types of slots depend both on the integrated controllers already existing on the motherboard and on the tasks to be solved on the PC.

MOTHERBOARD FORM FACTORS

Motherboards are classified according to what is known as the Form Factor. The form factor determines not only the size of motherboards, but also a number of specific characteristics that determine their functional and performance properties. Each form factor requires a different case and power supply. Today there are four prevailing motherboard sizes – AT, ATX, LPX and NLX.

1 AT form factor

The AT form factor is divided into two size variants – AT and Baby AT. The size of a full-size AT board is up to 12″ wide, which means that such a board is unlikely to fit into most of today’s cases. The drive and disk drive bays and power supply will certainly interfere with the installation of such a board. In addition, the positioning of the board components far away from each other may cause some problems when operating at high clock frequencies. Therefore, after motherboards for the 386 processor, this size is no longer found.

Thus the only AT form factor motherboards available on the market are the Baby AT size boards. The size of Baby AT boards is 8.5″ wide and 13″ long. Almost all have serial and parallel ports attached to the motherboard via connector strips. They also have a single DIN5-type keyboard connector soldered into the back of the board. A socket for the processor is mounted on the front side of the board. SIMM and DIMM slots are in different locations, although they are almost always at the top of the motherboard.

Today this format is slowly coming off the scene. Some firms still produce some of their models in two versions – Baby AT and the newer ATX, but this is happening less and less often. Not to mention just the usability – so, most often on Baby AT boards all the connectors are gathered in one place, as a result of which either the cables from the communication ports are practically pulled through the whole motherboard to the back of the case, or from the IDE and FDD ports to the front. Memory module slots that go almost under the power supply. With limited freedom of action inside a very small space of MiniTower, it is, to say the least, uncomfortable. In addition, unsuccessfully solved the problem with cooling – the air does not come directly to the most in need of cooling part of the system – the processor.

Advantages:

1. well-organized standardization, widely deployed production allows a wide range of cases and power supplies;

2. the design is simple and inexpensive to produce.

Disadvantages:

1. inefficient cooling of modern components, there may be a need for additional fans;

2. The positioning of the processor may cause problems with installation of long extension boards, for example, full-size – 330×120 mm;

3. I/O connectors are connected to the motherboard through a large number of appropriate cables which have multiple pinning standards.

2 LPX form factor

Even before the advent of ATX, the first result of attempts to reduce PC costs was the LPX form factor. Designed for use in small cases to build low-cost PCs. The problem was solved by a rather innovative proposal: the introduction of the rack. Instead of inserting the expansion cards directly into the motherboard, in this variant they fit into a vertical rack connected to the board, parallel to the motherboard. This significantly reduced the height of the case because it is the height of the expansion cards that usually affects this parameter. The price for compactness is the maximum number of cards that can be connected – 2 or 3. Another innovation that has been widely used on LPX boards is a video chip integrated on the motherboard. The LPX case size is 9 x 13”, for the Mini LPX – 8 x 10”. Of course, this form factor was not intended to be a broad replacement for the Baby AT in mainstream MS: its purpose was for low-cost systems. Then came the NLX form factor, which began to supplant the LPX.

3 ATX form factor.

Not surprisingly, the ATX form factor in all its modifications became popular. The ATX specification, proposed by Intel back in 1995, aimed just at correcting all those shortcomings, which were revealed over time in the AT form factor. And the solution, in fact, was very simple – to turn the Baby AT board by 90 degrees, and make appropriate adjustments in the design. By that time Intel already had experience in this area – the LPX form factor. The ATX was just the epitome of the best features of both Baby AT and LPX: expandability was taken from Baby AT, and from LPX – high integration of components. The result is as follows:

* Integrated I/O port connectors. All modern motherboards have I/O connectors on the board, so it was a natural decision to put connectors on the board as well, which leads to a fairly significant reduction of wiring inside the case. Moreover at the same time among the traditional parallel, serial and keyboard connectors, there was also a place for the newcomers – PS/2 and USB ports. Furthermore, the cost of the motherboard has also decreased slightly by reducing the number of cables included.

* The accessibility of memory modules was significantly improved. As a result of all the changes, the memory slots were moved further away from the motherboard slots, CPU and power supply. As a result, upgrading the memory has become a minute affair in any case, while on Baby AT motherboards you sometimes have to take a screwdriver.

* Reduced distance between motherboard and drives. The connectors of IDE and FDD controllers have been moved almost close to the devices connected to them. This allows us to shorten the cable length and make the system more reliable.

* Separation of CPU and expansion slot. The CPU socket has been moved from the front of the board to the back, next to the power supply. This allows for the installation of full sized boards in the expansion slots – the CPU does not interfere with them. Also, the cooling problem has been solved – now the air sucked from the power supply blows directly on the processor.

The interface with the power supply has been improved. It now uses one 20-pin connector instead of two, like on AT boards. In addition, the motherboard is now able to control the power supply by turning it on at the right time or according to a certain event, turning it on from the keyboard, turning it off by the operating system, etc.

* 3.3V supply voltage. Now the 3.3V supply voltage, which is very widely used in modern system components (take PCI cards for example) comes from a power supply. AT boards used a motherboard-mounted AVR to provide it. In ATX boards there is no need for it.

Advantages:

1. the design of the power supply and the positioning of the processor and memory provide an effective cooling system for the elements;

2. easy access to memory and processor for upgrading;

The I/O connectors are fixed on the board and there are no problems with installation.

Disadvantages:

1. special, more complex and expensive power supply and case are needed compared to AT;

2. the complicated design of the motherboard, which affects its price.

For motherboards for Pentium 4 processors ATX standard has a difference, it is called ATX 2.03 or ATX12V. For such boards is different in the first place power supply, it must have the appropriate connectors to connect to a P4-board. The mod legislator (Intel) prescribes three power connectors on the board for Pentium 4: “standard” ATX (position 1 in the figures), “square” 4-Pin ATX12V (position 2 in the figure), and 5-pin “half AT connector” (AUXPWR) (position 3 in the figure).

Thus, if the board is not designed to work if all the necessary connectors are not connected to the power connectors, it will simply refuse to work. However, even if there is no hard start locking, the threat of unstable operation is still present. Some boards instead of ATX12V and AUXPWR have a power connector, which is already familiar to you (used to connect a standard HDD/CDROM), which removes some of the problems with power stability. Thus, before you start your experiments it makes sense to find out whether it makes sense to start them at all: maybe your Pentium 4 board will not work with the old PSU anyway.

Modern motherboards use colored connectors for plugging in external devices to meet the requirements of the PC99 specification.

One of the I/O connector layouts on an ATX motherboard with integrated audio.

4 Micro ATX form factor

ATX form factor was developed in the heyday of Socket 7 systems, and many of its features today are somewhat out of date. For example, a typical combination of slots, which was the basis for the specification, looked like 3 ISA/3 PCI/1 adjacent. Somewhat irrelevant today, isn’t it? ISA, no AGP, AMR, etc. Then again, 7 slots are not used 99% of the time anyway, especially today with chipsets like MVP4, SiS 620, i810, and other upcoming similar products. All in all, for a cheap ATX PC it’s a waste of resources. Based on similar considerations, the micro ATX format specification was introduced in December 1997, a modification of the ATX board designed for 4 slots for expansion boards.

Advantages:

1. smaller size compared to ATX, reducing the price of the board;

2. thanks to power supply design and layout of CPU and memory, an efficient cooling system is ensured;

3. easy access to memory and CPU

4. the I/O connectors are located on the board, making it easy to assemble and configure;

5. standard ATX or smaller Mini ATX can be used as a case and power supply.

Disadvantages:

1. the change in size entailed a reduction in the number of expansion slots;

2. the complicated design of the motherboard, which affects its price.

5 NLX Form Factor

The NLX form factor is aimed at low-profile cases. Both technical (e.g. the introduction of AGP and DIMMs, and the integration of audio/video components on the motherboard) and serviceability concerns were taken into account. For example, to assemble / disassemble many systems based on this form factor, a screwdriver is not required at all.

NLX features:

* An expansion card rack located on the right edge of the board. The motherboard is easy to detach from the stand and slide out of the chassis to change the CPU or memory, for example.

* The processor located in the left front corner of the board, directly opposite the fan.

* Generally grouping tall components, like CPU and memory, at the left end of the board to allow full-size expansion cards to be placed on the rack.

* Locating single-height (in the expansion card area) and double-height I/O connector blocks at the back end of the board, to accommodate the maximum number of connectors.

Generally speaking, the rack is a very interesting thing. Actually it is one motherboard divided into two parts – the part where the system components actually are and the part connected to it through 340 pin connector at an angle of 90 degrees which houses all sorts of I/O components – expansion cards, port connectors, data drives, where the power is connected. Thus, firstly, increased serviceability – there is no need to access unnecessary components at the moment. Secondly, manufacturers have more flexibility as a result – one model of the main board and a rack for each specific customer is made, with the integration of the necessary components on it. Does this description remind you of anything at all?

Advantages:

1. easy access to the motherboard for upgrades;

2. The board is designed so that it can easily be removed from the case;

3. The cross-board is used as the central unit.

Disadvantages:

1. special (NLX) case and power supply are required.

ADDITIONAL INTEGRATED TECHNOLOGIES

1. AMR (other similar standard CNR and ACR).

An alternative (and promising) way to partially integrate audio and modem on the motherboard is to implement AMP. This combination stands for Audio-Modem Riser. Practically it is an implementation of the AC’97 specifications. What was formerly called the Digital AC’97 Controller is now renamed AMR – a controller that is built directly into the chipset support. The motherboard carries a common part of the modem and sound card, namely the DAC and ADC. On the motherboard also appears very short (only 46 pins) slot, where the special card is inserted. And already on the card there are other blocks to implement the functions of the modem and sound card. There will be very few of them – a couple of specialized DSP and analog parts (such as amplifier). The card will also have all the external connectors: for connecting speakers, microphones, phone line, phone, or maybe just a phone handset, etc.

2 Hardware monitoring.

Hardware monitoring, integrated into the chipset or implemented on the motherboard as a separate chip, will help to monitor the state of the most important operating parameters. It allows to get information about chip voltages, fans rotation speed, processor and motherboard temperatures. When critical temperatures are reached it is possible to warn the user or even shut down the computer

2 IrDA connector.

The IrDA connector is the connector for the infrared receiver/transmitter. The physical connection is made to one of the COM ports (usually COM2), and by connecting an optional board it is possible to communicate with any device equipped with a similar receiver/transmitter. Infrared communication allows you to connect up to one meter in the point-to-point mode and uses an infrared range from 850 to 900nm. Communication between devices is established in half duplex mode.

3 Dual BIOS technology.

The use of this technology allows to significantly improve the reliability of the computer, because in the case of failure of a chip with BIOS, its role is taken by the second, the spare chip. Here is a brief explanation that the BIOS is a chip that links the components of the motherboard and expansion cards into a single unit. Roughly speaking, it is the “spinal cord” of the computer. This program is written in a special chip installed on the motherboard. When you turn off the power this program is not erased. But to be able to quickly change it in the case of a new device (for example, a new modification of the processor), there is an option to “flash” this chip with an updated BIOS program by the user. Usually you can “download” a new BIOS to your computer via the Internet, from the motherboard manufacturer’s website.

4 Digital Video (DV) or, in other words, IEEE 1394 (i. LINK) interface.

This high-speed interface (up to 400 Mbps) is designed for high-speed transfer of large amounts of data in real time. Recently, it has become especially popular for transporting video streams. It is used, for example, to connect digital video cameras to the system. The latter, in this case, can be connected directly to the computer. Physically, the corresponding set of chips and connectors is available as a separate card to be installed in the slot (its price is about $100), or as a node integrated into the motherboard. The price of the motherboard, in this case, about $ 50 higher than usual. Therefore, it is better to decide to what extent you need IEEE 1394 before buying a motherboard.