Main Board Expansion Slots

An expansion card is an electronic circuit board that adds more functionality to a desktop computer.These cards are installed into the expansion slot of a computer motherboard, and they allow the computer to perform additional functions not offered by the motherboard. An expansion slot is a socket on the motherboard that is used to insert an expansion card (or circuit board), which provides additional features to a computer such as video, sound, advanced graphics, Ethernet or memory. Expansion slots are long and narrow slots which are located in the motherboard. You usually find the following types of expansion slots-Peripheral component.

Summary :

This essay from MiniTool will introduce you with 20 major components of a motherboard together with their basic information including their functions.

According to Wikipedia, a motherboard is the main printed circuit board (PCB) in common computers (both desktops and laptops) as well as other expandable systems. It is also known as a mainboard, main circuit board, system board, baseboard, logic board, planar board or mobo.

Motherboard Components and Their Functions

There are many components found in a motherboard. Some of them are major motherboard components while others are not. The following is a motherboard components list.

1. CPU (Central Processing Unit) chip

CPU is the electronic circuitry in a computer that executes instructions that make up a program. It is also known as a central processor or the main processor. The CPU executes the basic logic, arithmetic, controlling as well as input/output (I/O) operations specified by the instructions in the desktop programs.

2. RAM (Random Access Memory) slots

RAM is a kind of computer memory that can be read and written. It is mainly used to save data and machine code. A RAM device permits data to be read or written in nearly the same amount of time no matter where the data’s physical location is in the memory. Compared to the direct-access storage devices like hard drives, CD/DVD and magnetic tapes, RAM media is much faster for data reading and writing.

3. Southbridge/northbridge

They are the two chips in the core logic chipset on the motherboard. Typically, the southbridge implements the slower capabilities of the motherboard in a northbridge/southbridge chipset computer architecture.

The northbridge, also known as host bridge or Memory Controller Hub, is connected directly to the CPU via the front-side bus (FSB). It is responsible for tasks requiring the highest performance. Together with the southbridge, they manage communications between the CPU and other motherboard components.

4. BIOS (Basic Input/Output System)

BIOS, also called system BIOS, PC BIOS or ROM BIOS, is firmware that is used to perform hardware initialization during the booting process; and to provide runtime services for operating system and programs. The BIOS firmware is the first software to run when powered on; it is re-installed on a PC’s system board.

5. I/O port

Input/output ports are the connections between the CPU and peripheral devices on a motherboard. There are two complementary methods to perform input and output processes: memory-mapped I/O (MMIO) and port-mapped I/O (PMIO). Alternatively, you can use dedicated I/O processors, called channels on mainframe computers, which execute their own instructions.

6. USB (Universal Serial Bus)

USB is an industry standard that creates specifications for connectors, cables and protocols for connection; power supply (interfacing) and communication among computers, computer peripherals as well as other desktops. There are a great many USB hardware including several different connectors, of which USB-C is the latest kind.

7. CPU slot

A CPU slot, also called a CPU socket or Processor socket, contains one or more mechanical components that provide mechanical and electrical connections between the PCB and a microprocessor (CPU). Therefore, you can install a CPU on a motherboard without soldering.

8. PCI (Peripheral Component Interconnect) slot

Peripheral Component Interconnect is a local computer bus for connecting hardware to a computer. It supports all the functions of a processor bus. PCI is usually been called Conventional PCI to distinguish it from its successor PCI Express (PCIe, PCI-e or PCI-E).

PCI Express is a high-speed serial computer expansion bus standard designed to replace the older PCI, PCI-X and AGP bus standard. It is a general-use motherboard interface for the graphics card, SSDs, hard drives, Wi-Fi as well as Ethernet hardware connections.

This post tells you the differences between PCI and PCIe. It also shows you how to distinguish them.

9. AGP (Accelerated Graphics Port) slot

AGP was designed as a high-speed point-to-point channel for connecting a video card (graphics card) to a computer system. Primarily, it was used to assist in the acceleration of 3D computer graphics. AGP is originally designed to be a descendant of the PCI series of connections for video cards. Yet, it was replaced by the PCIe slots.

10. ISA (Industry Standard Architecture) slot

ISA is the 16-bit internal bus of IMB PC/AT and similar computers that are based on Intel 80286 and its immediate successors during the 1980s. It was backward compatible with the 8-bit bus of the 8088-based IBM PC largely.

There once was an attempt to extend ISA into a 32-bit bus, called Extended Industry Standard Architecture (EISA). The attempt wasn’t very successful and the EISA was largely replaced by the later VESA Local Bus and the PCI bus.

11. Parallel port

A parallel port is a kind of interface for attaching peripherals on desktops. The name of this kind of port is derived from the way the data is sent. That is, the parallel ports send multiple bits of data at the same time. Serial interfaces, on the contrary, send bits one data at once. To achieve parallel data transfer, there are multiple data lines in the parallel port cables. The parallel port cable is larger than the cable of a contemporary serial port, which only has one data line within.

12. FDC (Floppy-Disk Controller)

FDC is a special-purpose chip and associated disk controller circuitry. It controls and directs reading from and writing to a computer’s floppy disk drive (FDD).

13. IDE (Integrated Drive Electronics) controller

The devices used for connecting IDE, Ethernet, FireWire, USB and other systems can be called host adapter. So, the IDE controller refers to the host adapter. A host adapter, also called a host controller or a host bus adapter (HBA), connects a computer (acting as the host system) to other network and storage devices.

Do you think your IDE hard drive is too old and outdated? How to upgrade IDE to SATA HDD or SSD? There is a step-by-step tutorial to help you.

14. CMOS (Complementary Metal-oxide-semiconductor) battery

CMOS battery, also called memory battery, clock battery or real-time clock (RTC), is generally a CR2032 lithium coin cell. The lifespan of the CMOS battery is estimated to be three years when the power supply unit (PSU) is unplugged or switch off.

15. Power supply connector

A power supply provides the necessary electrical power to let the computer to work. It takes standard 110-Volt AC (Alternative Current) power to DC (Direct Current) power of 12 Volt, 5 Volt, 3.3 Volt, etc.

16. Mouse and keyboard ports

All computers have a keyboard port connected directly to the motherboard. There are two types of connectors. The oldest one is a special DIN (Deutsches Institut für Normung) connector while the newest one is the mini DIN PS/2-style connector. Many PCs use the PS/2-style connectors for both keyboard and mouse; and the connectors are marked clearly for different usage.

17. DIP (Dual In-line Package) switch

A DIP switch is a manual electric switch packaged with others in a standard dual in-line package. The term may refer to an individual switch or the whole unit. The DIP switch is designed to be used on a printed circuit board (motherboard) together with other electronic motherboard components. It is usually used to customize the behavior of an electronic device for specific situations.

18. Jumper

A jumper is a short length of conductor that is used to close, open or bypass part of an electronic circuit. Typically, jumpers are used to set up or configure printed circuit boards like the motherboard.

19. Heat sink/heatsink (cooling system)

A heat sink is a passive heat exchanger that transfers the heat generated by parts of motherboard into a fluid medium like liquid or air. The fluid medium will dissipate away from the device. Thus, the temperature of the device is kept within a tolerable range. On the motherboard, the heatsink is usually used to cool CPU, GPU (graphics processing unit), chipsets and RAM modules.

20. Clock generator

A clock generator is an electronic oscillator (circuit) that produces a clock signal for usage in synchronizing a circuit’s operation. The clock signal ranges between high and low frequencies, thus creating a metronome for the coordination of actions.

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What Are the Two Main Components on the Motherboard?

After reading the above contents, you can figure out that the two main components on the motherboard are CPU and RAM. They also list in the first two locations in the above. Actually, the above motherboard components are listed mainly based on their importance on the motherboard. Yet, that is just our personal opinion. Those components’ importance is different in different situations.

^[1]In computing, an expansion card, also known as an expansion board, adapter card or accessory card, is a printed circuit board that can be inserted into an electrical connector, or expansion slot, on a computer motherboard, backplane or riser card to add functionality to a computer system via the expansion bus.

Expansion cards allow the capacities and interfaces of a computer system to be adjusted to the tasks it will perform. For example, a high-speed multi-channel data acquisition system would be of no use to a personal computer used for bookkeeping, but might be a key part of a system used for industrial process control. Expansion cards can often be installed or removed in the field, allowing a degree of user customization for particular purposes. Some expansion cards take the form of 'daughterboards' that plug into connectors on a supporting system board.

In personal computing, notable expansion buses and expansion card standards include the S-100 bus from 1974 associated with the CP/Moperating system, the 50-pin expansion slots of the original Apple II computer from 1977 (unique to Apple), IBM's Industry Standard Architecture (ISA) introduced with the IBM PC in 1981, Acorn's tube expansion bus on the BBC Micro also from 1981, IBM's patented and proprietary Micro Channel architecture (MCA) from 1987 that never won favour in the clone market, the vastly improved Peripheral Component Interconnect (PCI) that displaced ISA in 1992, and PCI Express from 2003 which abstracts the interconnect into high-speed communication 'lanes' and relegates all other functions into software protocol.

History[edit]

Even vacuum-tube based computers had modular construction, but individual functions for peripheral devices filled a cabinet, not just a printed circuit board. Processor, memory and I/O cards became feasible with the development of integrated circuits. Expansion cards allowed a processor system to be adapted to the needs of the user, allowing variations in the type of devices connected, additions to memory, or optional features to the central processor (such as a floating point unit). Minicomputers, starting with the PDP-8, were made of multiple cards, all powered by and communicating through a passive backplane.

The first commercial microcomputer to feature expansion slots was the Micral N, in 1973. The first company to establish a de facto standard was Altair with the Altair 8800, developed 1974–1975, which later became a multi-manufacturer standard, the S-100 bus. Many of these computers were also passive backplane designs, where all elements of the computer, (processor, memory, and I/O) plugged into a card cage which passively distributed signals and power between the cards.

Proprietary bus implementations for systems such as the Apple II co-existed with multi-manufacturer standards.

IBM PC and descendants[edit]

IBM introduced what would retroactively be called the Industry Standard Architecture (ISA) bus with the IBM PC in 1981. At that time, the technology was called the PC bus. The IBM XT, introduced in 1983, used the same bus (with slight exception). The 8-bit PC and XT bus was extended with the introduction of the IBM AT in 1984. This used a second connector for extending the address and data bus over the XT, but was backward compatible; 8-bit cards were still usable in the AT 16-bit slots. Industry Standard Architecture (ISA) became the designation for the IBM AT bus after other types were developed. Users of the ISA bus had to have in-depth knowledge of the hardware they were adding to properly connect the devices, since memory addresses, I/O port addresses, and DMA channels had to be configured by switches or jumpers on the card to match the settings in driver software.

IBM's MCA bus, developed for the PS/2 in 1987, was a competitor to ISA, also their design, but fell out of favor due to the ISA's industry-wide acceptance and IBM's licensing of MCA. EISA, the 32-bit extended version of ISA championed by Compaq, was used on some PC motherboards until 1997, when Microsoft declared it a 'legacy' subsystem in the PC 97 industry white-paper. Proprietary local buses (q.v. Compaq) and then the VESA Local Bus Standard, were late 1980s expansion buses that were tied but not exclusive to the 80386 and 80486 CPU bus.^[2][3][4] The PC/104 bus is an embedded bus that copies the ISA bus.

Intel launched their PCI bus chipsets along with the P5-based Pentium CPUs in 1993. The PCI bus was introduced in 1991 as a replacement for ISA. The standard (now at version 3.0) is found on PC motherboards to this day. The PCI standard supports bus bridging: as many as ten daisy chained PCI buses have been tested. Cardbus, using the PCMCIA connector, is a PCI format that attaches peripherals to the Host PCI Bus via PCI to PCI Bridge. Cardbus is being supplanted by ExpressCard format.

Intel introduced the AGP bus in 1997 as a dedicated video acceleration solution. AGP devices are logically attached to the PCI bus over a PCI-to-PCI bridge. Though termed a bus, AGP usually supports only a single card at a time (LegacyBIOS support issues). From 2005 PCI-Express has been replacing both PCI and AGP. This standard, approved^{[Like whom?]} in 2004, implements the logical PCI protocol over a serial communication interface. PC/104(-Plus) or Mini PCI are often added for expansion on small form factor boards such as Mini-ITX.

For their 1000 EX and 1000 HX models, Tandy Computer designed the PLUS expansion interface, an adaptation of the XT-bus supporting cards of a smaller form factor. Because it is electrically compatible with the XT bus (a.k.a. 8-bit ISA or XT-ISA), a passive adapter can be made to connect XT cards to a PLUS expansion connector. Another feature of PLUS cards is that they are stackable. Another bus that offered stackable expansion modules was the 'sidecar' bus used by the IBM PCjr. This may have been electrically comparable to the XT bus; it most certainly had some similarities since both essentially exposed the 8088 CPU's address and data buses, with some buffering and latching, the addition of interrupts and DMA provided by Intel add-on chips, and a few system fault detection lines (Power Good, Memory Check, I/O Channel Check). Again, PCjr sidecars are not technically expansion cards, but expansion modules, with the only difference being that the sidecar is an expansion card enclosed in a plastic box (with holes exposing the connectors).

Other families[edit]

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Most other computer lines, including those from Apple Inc. (Apple II, Macintosh), Tandy, Commodore, Amiga, and Atari, offered their own expansion buses. The Amiga used Zorro II. Apple used a proprietary system with seven 50-pin-slots for Apple II peripheral cards, then later used the NuBus for its Macintosh series until 1995, when they switched to a PCI Bus. Generally, PCI expansion cards will function on any CPU platform if there is a software driver for that type. PCI video cards and other cards that contain a BIOS are problematic, although video cards conforming to VESA Standards may be used for secondary monitors. DEC Alpha, IBM PowerPC, and NEC MIPS workstations used PCI bus connectors.^[5] Both Zorro II and NuBus were plug and play, requiring no hardware configuration by the user.

Even many video game consoles, such as the Sega Genesis, included expansion buses; at least in the case of the Genesis, the expansion bus was proprietary, and in fact the cartridge slots of many cartridge based consoles (not including the Atari 2600) would qualify as expansion buses, as they exposed both read and write capabilities of the system's internal bus. However, the expansion modules attached to these interfaces, though functionally the same as expansion cards, are not technically expansion cards, due to their physical form.

Other computer buses were used for industrial control, instruments, and scientific systems. Some of these standards were VMEbus, STD Bus, and others.

External expansion buses[edit]

Laptops generally are unable to accept most expansion cards. Several compact expansion standards were developed. The original PC Card expansion card standard is essentially a compact version of the ISA bus. The CardBus expansion card standard is an evolution of the PC card standard to make it into a compact version of the PCI bus. The original ExpressCard standard acts like it is either a USB 2.0 peripheral or a PCI Express 1.x x1 device. ExpressCard 2.0 adds SuperSpeed USB as another type of interface the card can use. Unfortunately, CardBus and ExpressCard are vulnerable to DMA attack unless the laptop has an IOMMU that is configured to thwart these attacks.

Applications[edit]

The primary purpose of an expansion card is to provide or expand on features not offered by the motherboard. For example, the original IBM PC did not have on-board graphics or hard drive capability. In that case, a graphics card and an ST-506 hard disk controller card provided graphics capability and hard drive interface respectively. Some single-board computers made no provision for expansion cards, and may only have provided IC sockets on the board for limited changes or customization. Since reliable multi-pin connectors are relatively costly, some mass-market systems such as home computers had no expansion slots and instead used a card-edge connector at the edge of the main board, putting the costly matching socket into the cost of the peripheral device.

In the case of expansion of on-board capability, a motherboard may provide a single serial RS232 port or Ethernet port. An expansion card can be installed to offer multiple RS232 ports or multiple and higher bandwidth Ethernet ports. In this case, the motherboard provides basic functionality but the expansion card offers additional or enhanced ports.

Physical construction[edit]

One edge of the expansion card holds the contacts (the edge connector or pin header) that fit into the slot. They establish the electrical contact between the electronics on the card and on the motherboard. Peripheral expansion cards generally have connectors for external cables. In the PC-compatible personal computer, these connectors were located in the support bracket at the back of the cabinet. Industrial backplane systems had connectors mounted on the top edge of the card, opposite to the backplane pins.

Depending on the form factor of the motherboard and case, around one to seven expansion cards can be added to a computer system. 19 or more expansion cards can be installed in backplane systems. When many expansion cards are added to a system, total power consumption and heat dissipation become limiting factors. Some expansion cards take up more than one slot space. For example, many graphics cards on the market as of 2010 are dual slot graphics cards, using the second slot as a place to put an active heat sink with a fan.

Some cards are 'low-profile' cards, meaning that they are shorter than standard cards and will fit in a lower height computer chassis. (There is a 'low profile PCI card' standard^[1] that specifies a much smaller bracket and board area). The group of expansion cards that are used for external connectivity, such as network, SAN or modem cards, are commonly referred to as input/output cards (or I/O cards).

Daughterboard[edit]

A daughterboard, daughtercard, mezzanine board or piggyback board is an expansion card that attaches to a system directly.^[6] Daughterboards often have plugs, sockets, pins or other attachments for other boards. Daughterboards often have only internal connections within a computer or other electronic devices, and usually access the motherboard directly rather than through a computer bus.

Daughterboards are sometimes used in computers in order to allow for expansion cards to fit parallel to the motherboard, usually to maintain a small form factor. This form are also called riser cards, or risers. Daughterboards are also sometimes used to expand the basic functionality of an electronic device, such as when a certain model has features added to it and is released as a new or separate model. Rather than redesigning the first model completely, a daughterboard may be added to a special connector on the main board. These usually fit on top of and parallel to the board, separated by spacers or standoffs, and are sometimes called mezzanine cards due to being stacked like the mezzanine of a theatre. Wavetable cards (sample-based synthesis cards) are often mounted on sound cards in this manner.

Some mezzanine card interface standards includethe 400 pin FPGA Mezzanine Card (FMC);the 172 pin High Speed Mezzanine Card (HSMC);^[7][8]the PCI Mezzanine Card (PMC);XMC mezzanines;the Advanced Mezzanine Card;IndustryPacks (VITA 4), the GreenSpring Computers Mezzanine modules;etc.

Examples of daughterboard-style expansion cards include:

• Enhanced Graphics Adapter piggyback board, adds memory beyond 64 KB, up to 256 KB^[9]
• Expanded memory piggyback board, adds additional memory to some EMS and EEMS boards^[10]
• ADD daughterboard
• RAID daughterboard
• Network interface controller (NIC) daughterboard
• CPU Socket daughterboard
• Bluetooth daughterboard
• Modem daughterboard
• AD/DA/DIO daughter-card
• Communication daughterboard (CDC)
• Server Management daughterboard (SMDC)
• Serial ATA connector daughterboard
• Robotic daughterboard
• Access control List daughterboard
• Arduino 'shield' daughterboards
• Beaglebone 'cape' daughterboard
• Raspberry Pi 'HAT add-on board'^[11]
• Network Daughterboard (NDB). Commonly integrates: bus interfaces logic, LLC, PHY and Magnetics onto a single board.

Standards[edit]

• PCI Extended (PCI-X)
• PCI Express (PCIe)
• Accelerated Graphics Port (AGP)
• Conventional PCI (PCI)
• Industry Standard Architecture (ISA)
• Micro Channel architecture (MCA)
• VESA Local Bus (VLB)
• CardBus/PC card/PCMCIA (for notebook computers)
• ExpressCard (for notebook computers)
• Audio/modem riser (AMR)
• Communications and networking riser (CNR)
• CompactFlash (for handheld computers and high speed cameras and camcorders)
• SBus (1990s SPARC-based Sun computers)
• Zorro (Commodore Amiga)
• NuBus (Apple Macintosh)

See also[edit]

• M-Module, an industrial mezzanine standard for modular I/O

References[edit]

1. ^ ^ab'PCI Mechanical Working Group ECN: Low Profile PCI Card'(PDF). Pcisig.com. Retrieved 2012-11-17.
2. ^'MB-54VP'. ArtOfHacking.com. Retrieved 2012-11-17.
3. ^'NX586'. ArtOfHacking.com. Retrieved 2012-11-17.
4. ^'LEOPARD 486SLC2 REV. B'. ArtOfHacking.com. Retrieved 2012-11-17.
5. ^'Motherboards'. Artofhacking.com. Retrieved 2012-11-17.
6. ^ IEEE Std. 100 Authoritative Dictionary of IEEE Standards Terms, Seventh Edition, IEEE, 2000,ISBN0-7381-2601-2, page 284
7. ^Jens Kröger.'Data Transmission at High Rates via Kapton Flexprints for the Mu3e Experiment'.2014.p. 43 to 44.
8. ^Altera.'High Speed Mezzanine Card (HSMC) Specification'.p. 2-3.
9. ^Market Looks to EGA as De Facto Standard, InfoWorld, Aug 19, 1985
10. ^Product Comparison: 16-Bit EMS Memory, InfoWorld, Sep 7, 1987
11. ^'Add-on boards and HATs'. GitHub. Raspberry Pi Foundation. Retrieved 19 June 2020.

External links[edit]