Glossary - Computer Motherboards

Motherboard Dimensions / Mounting Holes / Chipset / Processor slot/socket / AGP / PCI / ISA / RAM / Port / Serial / Parallel / PS/2 / USB / VGA / SCSI / Jumper / Connector header / Jumper header / BIOS / Driver / Cable set / Processor / System RAM / Chassis / Power Supply / Socket 7 / Socket 8 / Slot 1 / Slot 2 / Xeon / Cache / L1 Cache / L2 Cache / ACPI / SOHO / ECP / EPP / ECC / APM / DMI / SDRAM / EDO / DIMM / SIMM

Chipset Models Intel 810 / Intel 440BX / Intel 440GX / Intel 440LX / Intel 440ZX / ALi 1541 / SiS 530 / SiS 600 / VIA Apollo Pro

Form Factor Baby AT (BAT) / ATX / MicroATX

Motherboard - the principle printed circuit board assembly in a computer; includes core logic (chipset), interface sockets and/or slots, and input/output (I/O) ports.
Printed circuit board (PCB) - a thin, laminated sheet composed of a series of epoxy resin and copper layers and etched electronic circuits (signal, ground and power)
Chipset (or core logic) - two or more integrated circuits which control the interfaces between the system processor, RAM, I/O devises, and adapter cards.
Processor slot/socket - the slot or socket used to mount the system processor on the motherboard
AGP - Accelerated Graphics Port - a high speed interface for video cards; runs at 1X (66MHz), 2X (133MHz), or 4X (266MHz).
PCI - Peripheral Component Interconnect - a high speed interface for video cards, sound cards, network interface cards, and modems; runs at 33MHz.
ISA - Industry Standard Architecture - a relatively low speed interface primarily used for sound cards and modems; runs at approx. 8MHz.
RAM - Random Access Memory - see System RAM
Port (serial, parallel, PS/2, USB, sound, LAN, VGA, SCSI) - interface connectors for the associated types of devices
Serial - a low speed interface typically used for mice and external modems
Parallel - a low speed interface typically used for printers
PS/2 - a low speed interface used for mice and keyboards
USB - Universal Serial Bus - a medium speed interface typically used for mice, keyboards, scanners, display panels (control features, not data), speakers (control features, not sound), scanners, and some digital cameras.
VGA - Video Graphics Adapter - the interface from your video card or integrated video connector and the system display monitor.
SCSI (interface) - Small Computer System Interface - the interface between a SCSI controller and an external or internal SCSI device.
Jumper - a small block (approx .250" wide x .312" long x .125" thick with two holes running lengthwise which are connected with a metal structure), or the functionally equivalent electronic "interconnect"; used to enable, disable,  or select operating parameter on a motherboard or other PCB by either electrically connecting two pins on the PCB (closed) or separating them (open - only one pin is covered or the jumper is removed).
Connector header - a series of two or more metal pins on the motherboard or other PCB; used to attach a cable to indicator lights, switches, and/or other devices in the computer
Jumper header - two pins or a series of two-pin groups where jumpers are used.
BIOS - Pronounced "bye-ose," an acronym for basic input/output system. The BIOS is built-in software that determines what a computer can do without accessing programs from a disk. On PCs, the BIOS contains all the code required to control the keyboard, display screen, disk drives, serial communications, and a number of miscellaneous functions.
The BIOS is typically placed in a ROM chip that comes with the computer (it is often called a ROM BIOS). This ensures that the BIOS will always be available and will not be damaged by disk failures. It also makes it possible for a computer to boot itself. Because RAM is faster than ROM, though, many computer manufacturers design systems so that the BIOS is copied from ROM to RAM each time the computer is booted. This is known as shadowing.
Many modern PCs have a flash BIOS, which means that the BIOS has been recorded on a flash memory chip, which can be updated if necessary.
The PC BIOS is fairly standardized, so all PCs are similar at this level (although there are different BIOS versions). Additional DOS functions are usually added through software modules. This means you can upgrade to a newer version of DOS without changing the BIOS.
PC BIOSes that can handle Plug-and-Play (PnP) devices are known as PnP BIOSes, or PnP-aware BIOSes. These BIOSes are always implemented with flash memory rather than ROM.
Driver - software which defines the characteristics of a device for use by another device or other software
Cable set - one or more interface cables (typically, in relation to a motherboard, includes cables for a floppy drive, hard drive, and CD-ROM drive; may include cables between an internal connector header and a bracket or other opening at the front of rear of the system; may include cables for both IDE/ATAPI and SCSI devices).
Processor - the "central processing unit" (CPU); the principle integrated circuit used for doing the "computing" in "personal computing"
System RAM - the random access memory (RAM) used by the CPU for computational purposes
Chassis - the structure used to house the various "internal" components of the computer (i.e., the motherboard, adapter cards, various storage devices, power supply, etc.)  Normally called case.
Power Supply - the device used to convert, regulate, and transmit external power for use by the components housed inside the computer chassis.
Socket 7 - The form factor for fifth-generation CPU chips from Intel, Cyrix, and AMD. All Pentium chips, except Intel's Pentium Pro (Socket 8) and Pentium II (Slot 1), conform to the Socket 7 specifications. Intel has decided to phase out Socket 7 and replace it with Slot 1. But Intel's competitors, such as AMD and Cyrix, are sticking with Socket 7, and are developing an enhanced version.
Socket 8 - The form factor for Intel's Pentium Pro microprocessors. The Pentium Pro was the first microprocessor not to use the venerable Socket 7 form factor. The Pentium II microprocessors use an even newer form factor called Slot 1.
Socket 8 is a 387-pin ZIF socket with connections for the CPU and one or two SRAM dies for the Level 2 (L2) cache.
Slot 1 - The form factor for Intel's Pentium II processors. The Slot 1 package replaces the Socket 7 and Socket 8 form factors used by previous Pentium processors. Slot 1 is a 242-contact daughtercard slot that accepts a microprocessor packaged as a Single Edge Contact (SEC) cartridge. A motherboard can have one or two Slot 1s.
Slot 2 - A chip packaging design used in Intel's newer Pentium II chipsets, starting with the Xeon CPU. While the Slot 1 interface features a 242-contact connector, Slot 2 uses a somewhat wider 330-contact connector. The biggest difference between Slot 1 and Slot 2, though, is that the Slot 2 design allows the CPU to communicate with the L2 cache at the CPU's full clock speed. In contrast, Slot 1 only supports communication between the L2 cache and CPU at half the CPU's clock speed.
Xeon - A line of Pentium II chipsets from Intel introduced in 1998. Unlike previous Pentium II chips, which used a Slot 1 form factor, Xeon chips use Slot 2. This allows for faster data transfers between the CPU and L2 cache. Xeon chip speeds start at 400 MHz.
Cache - Pronounced cash, a special high-speed storage mechanism. It can be either a reserved section of main memory or an independent high-speed storage device. Two types of caching are commonly used in personal computers: memory caching and disk caching.
A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory. Memory caching is effective because most programs access the same data or instructions over and over. By keeping as much of this information as possible in SRAM, the computer avoids accessing the slower DRAM.
Some memory caches are built into the architecture of microprocessors. The Intel 80486 microprocessor, for example, contains an 8K memory cache, and the Pentium has a 16K cache. Such internal caches are often called Level 1 (L1) caches. Most modern PCs also come with external cache memory, called Level 2 (L2) caches. These caches sit between the CPU and the DRAM. Like L1 caches, L2 caches are composed of SRAM but they are much larger.
Disk caching works under the same principle as memory caching, but instead of using high-speed SRAM, a disk cache uses conventional main memory. The most recently accessed data from the disk (as well as adjacent sectors) is stored in a memory buffer. When a program needs to access data from the disk, it first checks the disk cache to see if the data is there. Disk caching can dramatically improve the performance of applications, because accessing a byte of data in RAM can be thousands of times faster than accessing a byte on a hard disk.
When data is found in the cache, it is called a cache hit, and the effectiveness of a cache is judged by its hit rate. Many cache systems use a technique known as smart caching, in which the system can recognize certain types of frequently used data. The strategies for determining which information should be kept in the cache constitute some of the more interesting problems in computer science.
L1 Cache - Short for Level 1 cache, a memory cache built into the microprocessor. See under cache. The L1 cache is also called the primary cache.
L2 Cache - Short for Level 2 cache, cache memory that is external to the microprocessor. In general, L2 cache memory, also called the secondary cache, resides on a separate chip from the microprocessor chip. The Pentium Pro, however, has an L2 cache on the same chip as the microprocessor.
ACPI - Short for Advanced Configuration and Power Interface, a power management specification developed by Intel, Microsoft, and Toshiba. ACPI, which will be part of the next version of Windows, enables the operating system to control the amount of power given to each device attached to the computer. With ACPI, the operating system can turn off peripheral devices, such as a CD-ROM players, when they're not in use. As another example, ACPI will enable manufacturers to produce computers that automatically power up as soon as you touch the keyboard.
APM - Short for Advanced Power Management, an API developed by Intel and Microsoft that allows developers to include power management in BIOSes. APM defines a layer between the hardware and the operating system that effectively shields the programmer from hardware details.
APM is expected to be gradually replaced by ACPI.
SOHO - Acronym for Small Office/Home Office, the fastest growing market for computer hardware and software. So-called SOHO products are specifically designed to meet the needs of professionals who work at home or in small offices.
ECP - Short for Extended Capabilities Port, a parallel-port standard for PCs that supports bi-directional communication between the PC and attached devices (such as a printer). ECP is about 10 times faster than the older Centronics standard.
Another modern parallel port for PCs that offers similar performance is the EPP (Enhanced Parallel Port).
EPP - Short for Enhanced Parallel Port, a parallel port standard for PCs that supports bi-directional communication between the PC and attached devices (such as a printer). EPP is about 10 times faster than the older Centronics standard.
Another modern parallel port for PCs that offers similar performance is the ECP (Extended Capabilities Port).
ECC - Short for Error-Correcting Code memory, a type of memory that includes special circuitry for testing the accuracy of data as it passes in and out of memory.
DMI - Short for Desktop Management Interface, an API to enable software to collect information about a computer environment. For example, using DMI a program can determine what software and expansion boards are installed on a computer.
DMI is designed to be platform -independent and operating system -independent so that programs can make the same function calls to collect information no matter what system they're running in. This system independence is implemented by collecting information from MIF files, which are plain text files containing information about a software or hardware component.
DMI was designed by the Desktop Management Task Force (DMTF), a consortium of hardware manufacturers led by Intel. Version 2.0 allows a central computer not only to gather information about computers connected to a network, but also to configure them. PCs that comply with DMI 2.0 are sometimes called managed PCs.
SDRAM - Short for Synchronous DRAM, a new type of DRAM that can run at much higher clock speeds than conventional memory. SDRAM actually synchronizes itself with the CPU's bus and is capable of running at 100 MHz, about three times faster than conventional FPM RAM, and about twice as fast EDO DRAM and BEDO DRAM. SDRAM is replacing EDO DRAM in many newer computers
Today's fastest Pentium systems use CPU buses running at 100 MHz, so SDRAM can keep up with them, though barely. Future PCs, however, are expected to have CPU buses running at 200 MHz or faster. SDRAM is not expected to support these high speeds which is why new memory technologies, such as RDRAM and SLDRAM, are being developed.
EDO - Short for Extended Data Output Dynamic Random Access Memory, a type of DRAM that is faster than conventional DRAM. Unlike conventional DRAM which can only access one block of data at a time, EDO RAM can start fetching the next block of memory at the same time that it sends the previous block to the CPU.
DIMM - Short for dual in-line memory module, a small circuit board that holds memory chips. A single in-line memory module (SIMM) has a 32-bit path to the memory chips whereas a DIMM has 64-bit path. Because the Pentium processor requires a 64-bit path to memory, you need to install SIMMs two at a time. With DIMMs, you can install memory one DIMM at a time.
SIMM - Acronym for single in-line memory module, a small circuit board that can hold a group of memory chips. Typically, SIMMs hold up 8 (on Macintoshes) or 9 (on PCs) RAM chips. On PCs, the ninth chip is often used for parity error checking. Unlike memory chips, SIMMs are measured in bytes rather than bits. SIMMs are easier to install than individual memory chips.
The bus from a SIMM to the actual memory chips is 32 bits wide. A newer technology, called dual in-line memory module (DIMM), provides a 64-bit bus. For modern Pentium microprocessors that have a 64-bit bus, you must use either DIMMs or pairs of SIMMs.

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Chipset Models - Today there are many chipset models in the marketplace. The most popular for mainstream desktop computers are Intel's 810, BX, LX, and ZX. There are also "third party" chipsets available from Acer Labs (ALi), Silicon Integrated Systems (SiS), and VIA Technologies (VIA). The latter are quite similar to their Intel counterparts but may add features not available in the Intel chipsets. The third party chipsets may also support non-Intel processors (like those from AMD and others that have a 100MHz data bus and use the "Socket 7" processor-to-motherboard socket). Intel also produces chipsets that support dual processors. [At the time this FAQ was prepared, only Intel was producing chipsets which support multiple processors.] The following are brief descriptions of the key features of the most popular primary Intel and third party chipsets as of the date this FAQ was prepared (mid-June '99).
Intel 810 - "Basic PC and Mainstream segments", supports 2 DIMM (max. 512MB), SDRAM only, ECC/parity not supported, integrated "direct" AGP, integrated graphics controller (enhanced i740), 66/100MHz data bus, Ultra ATA/66  device support.
Intel 440BX - "Performance segment", supports 4 DIMM (max 1GB),  SDRAM only, ECC/parity supported, AGP 2X, 66/100MHz data bus, Ultra ATA/33 device support; dual processor support.
Intel 440GX - "Workstation segment", supports 4 DIMM (max 2GB), SDRAM only, ECC/parity supported, AGP 2X, 100MHz data bus, Ultra ATA/33 device support; dual processor support; supports Pentium II/III and Pentium Xeon II/III (slot 2).
Intel 440LX - "Basic PC segment", supports 4 DIMM (max 512MB SDRAM, 1GB EDO), ECC/parity supported, AGP 2X, 66MHz data bus, Ultra ATA/33 device support; dual processor support
Intel 440ZX - "Mainstream segment", supports 2 DIMM (max 256MB), SDRAM only, ECC/parity not supported, AGP 2X, 66/100MHz data bus, Ultra ATA/33 device support.
ALi 1541 - mainstream (Socket 7), supports 3 DIMM, 100MHz data bus, AGP 2X
SiS 530 - mainstream (Socket 7), supports 3 DIMM, 100MHz data bus, AGP 2X, integrated graphics controller
SiS 600 - mainstream (Pentium II/III), supports 3 DIMM, 100MHz data bus, AGP 2X
VIA Apollo Pro - mainstream (Pentium II/III), supports 4 DIMM, 100MHz data bus, AGP 2X
 
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Form Factor - the physical layout of a motherboard in regards the relative position of the adapter card expansion slots, the number of those slots, the relative size of the motherboard, and the orientation of the board in the chassis . For the purpose of this FAQ, only the Baby AT (BAT), ATX, and MicroATX form factors will be considered.
Baby AT (BAT) - this is the oldest of the currently available, mainstream motherboard form factors. Its distinguishing features are its orientation in the chassis (the long axis goes from the back to the front of the chassis), the type of keyboard connector (typically referred to as a "large DIN" connector), the presence of AT or PS/2 power supply connectors (a series of 12 "blades" in one or two adjacent male connectors), and the implementation of the various I/O connectors (serial and parallel ports) via a bracket which goes into one of the adapter card slots at the rear of the chassis. Please note that in some motherboards there may also be an ATX power supply connector (a rectangular grouping of 20 small sockets in two adjacent rows of 10).
ATX - this is the most common of today's mainstream motherboard form factors. Its distinguishing features are its orientation in the chassis (the long axis goes from side-to-side at the rear of the chassis), the use of "integrated I/O connectors" (all the connectors are built into the motherboard and exit to the rear of the chassis through an "I/O shield" where they are grouped together), and only an ATX power supply connector is provided.
MicroATX - this is a variation of the ATX form factor. It is much shorter in its long axis than the ATX and has fewer adapter card slots (3 compared to the ATX with typically 7). Otherwise the features are the same as the ATX.

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