Computer form factor

阅读量：5278 次

发布时间：2019-06-14

本文共 48923 字，大约阅读时间需要 163 分钟。

Computer form factor

From Wikipedia, the free encyclopedia

(Redirected from )

For computers form factors both larger and smaller than desktop personal computers, see .

Computer form factors
Listed by size (mm)

In , the form factor is the specification of a motherboard - the dimensions, power supply type, location of mounting holes, number of ports on the back panel, etc. Specifically, in the industry, standard form factors ensure that parts are interchangeable across competing vendors and generations of technology, while in enterprise computing, form factors ensure that server modules fit into existing systems. Traditionally, the most significant specification is for that of the motherboard, which generally dictates the overall size of the . have been developed and implemented.

[]

Overview of form factors[]

Pictorial comparison of some common computer form factors.

A is the main within a typical , or . Its main functions are as follows:

To serve as a central backbone to which all other modular parts such as , , and can be attached as required to create a computer

To accept (on many motherboards) different components (in particular CPU and ) for the purposes of customization

To distribute to PC components

To electronically co-ordinate and interface the operation of the components

As new generations of components have been developed, the standards of motherboards have changed too; for example, with being introduced, and more recently . However, the standardized size and layout of motherboard have changed much more slowly, and are controlled by their own standards. The list of components a motherboard must include changes far more slowly than the components themselves. For example, controllers have changed many times since their introduction, with many manufacturers bringing out their own versions, but in terms of form factor standards, the requirement to allow for a north bridge has remained fairly static for many years.

Although it is a slower process, form factors do evolve regularly in response to changing demands. The original PC standard (AT [Intel's "Advanced Technology"]) was superseded in 1995 by the current industry standard (Advanced Technology Extended), which still dictates the size and design of the motherboard in most modern PCs. The latest update to the ATX standard was released in 2007. A divergent standard by manufacturer called (also known as ITX, and not to be confused with EPIC) is based upon smaller form factors and its own standards.

Differences between form factors are most apparent in terms of their intended market sector, and involve variations in size, design compromises and typical features. Most modern computers have very similar requirements, so form factor differences tend to be based upon subsets and supersets of these. For example, a desktop computer may require more sockets for maximal flexibility and many optional connectors and other features on board, whereas a computer to be used in a system may need to be optimized for heat and size, with additional plug-in cards being less common. The smallest motherboards may sacrifice CPU flexibility in favor of a fixed manufacturer's choice.

Comparisons[]

Tabular information[]

Form factor	Originated	Max. size	Notes (typical usage, Market adoption, etc.)
	1983	8.5 × 11 in 216 × 279 mm	Obsolete, see . The was the successor to the original , its first home computer. As the specifications were open, many motherboards were produced and it became a standard.
(Advanced Technology)	1984	12 × 11–13 in 305 × 279–330 mm	Obsolete, see . Created by IBM for the, an machine. Also known as Full AT, it was popular during the era of the microprocessor. Superseded by ATX.
	1985	8.5 × 10–13 in 216 × 254–330 mm	IBM's 1985 successor to the AT motherboard. Functionally equivalent to the AT, it became popular due to its significantly smaller size.
	1996	12 × 9.6 in 305 × 244 mm	Created by Intel in 1995. As of 2007, it is the most popular form factor for commodity motherboards. Typical size is 9.6 × 12 in although some companies extend that to 10 × 12 in.
		12 × 10.5 in 305 × 267 mm	Created by the (SSI) forum. Derived from the EEB and ATX specifications. This means that SSI CEB motherboards have the same mounting holes and the same IO connector area as ATX motherboards.
		12 × 13 in 305 × 330 mm	Created by the (SSI) forum. Derived from the EEB and ATX specifications. This means that SSI CEB motherboards have the same mounting holes and the same IO connector area as ATX motherboards, but SSI EEB motherboards do not.
		16.2 × 13 in 411 × 330 mm	Created by the (SSI) forum. Derived from the EEB and ATX specifications. This means that SSI CEB motherboards have the same mounting holes and the same IO connector area as ATX motherboards.
	1996	9.6 × 9.6 in 244 × 244 mm	A smaller variant of the ATX form factor (about 25% shorter). Compatible with most ATX cases, but has fewer slots than ATX, for a smaller unit. Very popular for desktop and computers as of 2007.
	2005	5.9 × 5.9 in 150 × 150 mm	Mini-ATX is slightly smaller than Micro-ITX. Mini-ATX motherboards were design with MoDT (Mobile on Desktop Technology) which adapt mobile CPUs for lower power requirement, less heat generation and better application capability.
	1999	9.0 × 7.5 in 228.6 × 190.5 mm max.	A subset of microATX developed by Intel in 1999. Allows more flexible motherboard design, component positioning and shape. Can be smaller than regular microATX.
	2001	6.7 × 6.7 in 170 × 170 mm max.	A small, highly-integrated form factor, designed for small devices such as and .
	2003	4.7 × 4.7 in 120 × 120 mm	Targeted at smart digital entertainment devices such as PVRs, , and Car PCs, and thin devices.
	2007	3.9 × 2.8 in 100 × 72 mm max.
	2007	2.953 × 1.772 in 75 × 45 mm
Neo-ITX	2012	170 × 85 × 35 mm	Used in the VIA Android PC
(Balanced Technology Extended)	2004	12.8 × 10.5 in 325 × 267 mm max.	A standard proposed by Intel as a successor to ATX in the early 2000s, according to Intel the layout has better cooling. BTX Boards are flipped in comparison to ATX Boards, so a BTX or MicroBTX Board needs a BTX case, while an ATX style board fits in an ATX case. The RAM slots and the PCI slots are parallel to each other. Processor is placed closest to the fan. May contain a CNR board.
(or )	2004	10.4 × 10.5 in 264 × 267 mm max.
	2004	8.0 × 10.5 in 203 × 267 mm max.
	2007	200 × 244 mm max.
	2007	200 × 170 mm max.
		66 × 85 mm	Used in and . Requires a baseboard.
		95 × 114 mm	Used in and . Requires a baseboard.
Basic		95 × 125 mm	Used in and . Requires a carrier board. Formerly referred to as ETXexpress by .
Compact		95 × 95 mm	Used in and . Requires a carrier board. Formerly referred to as microETXexpress by .
Mini		55 × 84 mm	Used in and . Requires a carrier board. Formerly referred to as nanoETXexpress by . Also known as COM Express Ultra and adheres to pin-outs Type 1 or Type 10
		58 × 65 mm	Used in and . Requires a carrier board.
(EATX)	Unknown	12 × 13 in 305 × 330 mm	Used in server systems. Typically used for server-class type motherboards with dual processors and too much circuitry for a standard ATX motherboard. The mounting hole pattern for the upper portion of the board matches ATX.
(EEATX)		13.68 × 13 in 347 × 330 mm	Used in server systems. Typically used for server-class type motherboards with dual processors and too much circuitry for a standard E.ATX motherboard.
	Unknown	9 × 11–13 in 229 × 279–330 mm	Based on a design by , it allowed smaller cases than the AT standard, by putting the expansion card slots on a . Used in slimline retail PCs. LPX was never standardized and generally only used by large .
	Unknown	8–9 × 10–11 in 203–229 × 254–279 mm	Used in slimline retail PCs.
	1992	3.8 × 3.6 in	Used in embedded systems. AT Bus (ISA) architecture adapted to vibration-tolerant .
	1997	3.8 × 3.6 in	Used in embedded systems. PCI Bus architecture adapted to vibration-tolerant header connectors.
	2008	3.8 × 3.6 in	Used in embedded systems. PCI Express architecture adapted to vibration-tolerant header connectors.
	2008	3.8 × 3.6 in	Used in embedded systems. PCI/104-Express without the legacy PCI bus.
	1999	8–9 × 10–13.6 in 203–229 × 254–345 mm	A low-profile design released in 1997. It also incorporated a for expansion cards, and never became popular.
UTX	TQ-Components 2001	88 × 108 mm	Used in and IPCs. Requires a baseboard.
	1998	14 × 16.75 in 355.6 × 425.4 mm	A large design for servers and high-end workstations featuring multiple and .
	Unknown	16.48 × 13 in 418 × 330 mm	A proprietary design for servers and high-end workstations featuring multiple .
	2008	13.6 × 15 in 345.44 × 381 mm	A large design by currently featured on two motherboards; the eVGA SR2 and SRX. Intended for use with multiple . Cases require 9 expansion slots to contain this form-factor.
	2005	95 × 114 mm	Used in embedded systems. Requires a baseboard.

Graphical comparison of physical sizes[]

Maximum number of PCI/AGP/PCIe slots[]

ATX case compatible:

Specification	Number
	9
	7
	4
	3
	2
/	2
	1

Visual examples of different form factors[]

Different form factors

ATX
( KT7)

mini-ITX
(VIA EPIA 5000AG)

Pico-ITX
(VIA EPIA PX10000G)

PC/104 and EBX[]

is an embedded computer standard which defines both a form factor and computer bus. PC/104 is intended for embedded computing environments. Single board computers built to this form factor are often sold by vendors, which benefits users who want a customized rugged system, without months of design and paper work.

The PC/104 form factor was standardized by the PC/104 Consortium in 1992.[3] An IEEE standard corresponding to PC/104 was drafted as IEEE P996.1, but never ratified.

The 5.75 × 8.0 in (EBX) specification, which was derived from Ampro's proprietary Little Board form-factor, resulted from a collaboration between Ampro and .

As compared with PC/104 modules, these larger (but still reasonably embeddable) SBCs tend to have everything of a full PC on them, including application oriented interfaces like audio, analog, or digital I/O in many cases. Also it's much easier to fit Pentium CPUs, whereas it's a tight squeeze (or expensive) to do so on a PC/104 SBC. Typically, EBX SBCs contain: the CPU; upgradeable RAM subassemblies (e.g., DIMM); Flash memory for solid state disk; multiple USB, serial, and parallel ports; onboard expansion via a PC/104 module stack; off-board expansion via ISA and/or PCI buses (from the PC/104 connectors); networking interface (typically Ethernet); and video (typically CRT, LCD, and TV).

Mini PC[]

is a form factor very close in size to an external or .

Examples[]

ATX

From Wikipedia, the free encyclopedia

(Redirected from )

This article is about the computer form factor. For other uses, see .

This article may be in need of reorganization to comply with Wikipedia's . Please help by to make improvements to the overall structure. (September 2012)

An ATX motherboard


Listed by size (mm)
ATX (305×244)

ATX (Advanced Technology eXtended) is a specification developed by in 1995 to improve on previous like the . It was the first major change in , and design in many years, improving standardization and interchangeability of parts. The specification defines the key mechanical dimensions, mounting point, I/O panel, power and connector interfaces between a , a and a . With the improvements it offered, including lower costs, ATX overtook completely as the default form factor for new systems within a few years. ATX addressed many of the AT form factors annoyances that had frustrated system builders. Other standards for smaller boards (including , and ) usually keep the basic rear layout but reduce the size of the board and the number of expansion slots. In 2003, Intel announced the standard, intended as a replacement for ATX. As of 2009, the ATX form factor remains a standard for do-it-yourselfers; has however made inroads into pre-made systems. This^[] was designed to solve the problems in and motherboards.^[]

The official specifications were released by Intel in 1995 and have been revised numerous times since, the most recent being version 2.3, released in 2007.

A full-size ATX board is 12 × 9.6 in (305 × 244 mm). This allows many ATX form factor chassis to accept boards as well.

[]

Connectors[]

The original AT standard only had a single keyboard port opening on the back of the case. Any additional connectors such as video, audio, printer, serial, network and so forth would require either mounting in a slot or using custom-cut holes.

ATX I/O plates for motherboard rear connectors

On the back of the computer case, some major changes were made to the AT standard. Originally AT style cases had only a connector and expansion slots for add-on card backplates. Any other onboard interfaces (such as and ) had to be connected via to connectors which were mounted either on spaces provided by the case or brackets placed in unused expansion slot positions. ATX allowed each motherboard manufacturer to put these ports in a rectangular area on the back of the system with an arrangement they could define themselves, though a number of general patterns depending on what ports the motherboard offers have been followed by most manufacturers. Cases are usually fitted with a snap-out panel, also known as an I/O plate or I/O shield, in one of the common arrangements. If necessary, I/O plates can be replaced to suit a motherboard that is being fitted; the I/O plates are usually included with motherboards not designed for a particular computer. The computer will operate correctly without a plate fitted, although there will be open gaps in the case and the EMI/RFI screening will be compromised. Panels were made that allowed fitting an AT motherboard in an ATX case.

ATX also made the keyboard and mouse connectors ubiquitous. AT systems used a 5-pin for the keyboard and were generally used with serial port mice (although PS/2 mouse ports were also found on some systems). Many modern motherboards are phasing out the PS/2-style keyboard and mouse connectors in favor of the more modern . Other legacy connectors that are slowly being phased out of modern ATX motherboards include 25-pin and 9-pin . In their place are onboard peripheral ports such as , , , (both analog and ), video (analog , , , or ) and extra ports.

Variants[]

ATX motherboard size comparison; rear is on left.

(229 × 191 mm)

/Embedded ATX

(244 × 244 mm)

Mini ATX

(284 × 208 mm)

Standard ATX

(305 × 244 mm)

Extended ATX (EATX)

(305 × 330 mm)

(356 × 425 mm)

Several ATX-derived form factors have been specified that use the same power supply, mountings and basic back panel arrangement, but set different standards for the size of the board and number of expansion slots. Standard ATX provides seven slots at 0.8 in (20 mm) spacing; the popular Micro-ATX size removes 2.4 inches and three slots, leaving four. Here width refers to the distance along the external connector edge, while depth is from front to rear. Note each larger size inherits all previous (smaller) colors area.

Name	Form factor (width × depth)	Color in image
	9 × 7.5 in (229 × 191 mm)
and EmbATX	9.6 × 9.6 in (244 × 244 mm)
Mini ATX	11.2 × 8.2 in (284 × 208 mm)
Standard ATX	12 × 9.6 in (305 × 244 mm)
EATX (extended ATX)	12 × 13 in (305 × 330 mm)
(workstation ATX)	14 × 16.75 in (356 × 425 mm)

Note: has conflated the term with a more recent 15 × 15 cm (5.9 × 5.9 in) form factor. Since references to Mini ATX have been removed from ATX specifications since the adoption of microATX, the AOpen definition is the more contemporary term and the one listed above is apparently only of historical significance.

Larger variants[]

A number of manufacturers have added one, two or three additional expansion slots (at the standard 0.8 inch spacing) to the standard 12-inch ATX motherboard width.

SSI CEB[]

Main article:

Server System Infrastructure (SSI) Forum's Compact Electronics Bay (CEB) form factor measures 12 × 10.5 in (305 × 267 mm).

E-ATX/SSI EEB[]

Although true E-ATX is 12 × 13 in (305 × 330 mm) most motherboard manufacturers also refer to motherboards with measurements 12 × 10.1 in (305 × 257 mm), 12 × 10.4 in (305 × 264 mm), 12 × 10.5 in (305 × 267 mm) and 12 × 10.7 in (305 × 272 mm) as E-ATX.

EE-ATX[]

's server motherboard's measuring 13.68 × 13 in (347 × 330 mm).

Ultra ATX[]

Main article:

In 2008, unveiled a Foxconn F1 motherboard prototype, which has the same width as a standard ATX motherboard, but an extended 14.4" length to accommodate 10 slots. The firm called the new 14.4 × 9.6 in (366 × 244 mm) form factor for this motherboard "Ultra ATX" in its CES 2008 showing. Also unveiled during the January 2008 CES was the Armorsuit PC-P80 case with 10 slots designed for the motherboard.

XL-ATX[]

The name "XL-ATX" has been used by at least three companies in different ways.

In September 2009, had already released a 13.5 × 10.3 in (343 × 262 mm) "XL-ATX" motherboard as its EVGA X58 Classified 4-Way SLI.

In Q2/2010, Gigabyte launched another XL-ATX Mainboard with model number GA-X58A-UD9 in 2010 at 13.6 × 10.3 in (345 × 262 mm) and GA-X79-UD7 in 2011 at 12.8 × 10.0 in (324 × 253 mm). In April 2010, announced its 12.8 × 9.6 in (325 × 244 mm) GA-890FXA-UD7 motherboard that allowed all seven slots to be moved downward by one slot position. The added length could have allowed placement of up to eight expansion slots, but the top slot position is vacant on this particular model.

released MSI X58 Big Bang in 2010, MSI P67 Big Bang Marshal in 2011, MSI X79 Xpower Big Bang 2 in 2012 and MSI Z87 Xpower in 2013 all of them are 13.6 × 10.4 in (345 × 264 mm). Although these boards have room for additional expansion slots (9 and 8 total, respectively), all three provide only seven expansion connectors; the topmost positions are left vacant to provide more room for the CPU, chipset and associated cooling.

HPTX[]

In 2010, released a new motherboard, the "Super Record 2", or SR-2, whose size surpasses that of the "EVGA X58 Classified 4-Way SLI". The new board is designed to accommodate two Dual QPI LGA1366 socket CPUs (e.g. ), similar to that of the motherboard that could accommodate two Intel Core 2 Quad processors and has a total of seven PCI-E slots and 12 DDR3 RAM slots. The new form factor is dubbed "HPTX" and is 13.6 × 15 in (345 × 381 mm).

SSI MEB[]

Server motherboards measuring 16.2 × 13 in (411 × 330 mm).

SWTX[]

Main article:

's SWTX (Server / Workstation Technology eXtended) form factor measuring from 16 × 13 in (406 × 330 mm) to 18 × 13 in (457 × 330 mm). Most SWTX boards seem to be in the middle of this range around 16.48 × 13 in (419 × 330 mm).

WTX[]

Main article:

Intel's discontinued WTX (Workstation Technology Extended) form factor measuring 14 × 16.75 in (356 × 425 mm).

Power supply[]

24-pin ATX12V 2.x power supply connector

(20-pin omits the last four: 11, 12, 23 and 24)
Color	Signal	Pin	Pin	Signal	Color
Orange	+3.3 V	1	13	+3.3 V	Orange
+3.3 V sense	Brown
Orange	+3.3 V	2	14	−12 V	Blue
Black	Ground	3	15	Ground	Black
Red	+5 V	4	16	Power on	Green
Black	Ground	5	17	Ground	Black
Red	+5 V	6	18	Ground	Black
Black	Ground	7	19	Ground	Black
Grey		8	20	Reserved	N/C
Purple	+5 V standby	9	21	+5 V	Red
Yellow	+12 V	10	22	+5 V	Red
Yellow	+12 V	11	23	+5 V	Red
Orange	+3.3 V	12	24	Ground	Black
Pins 8, and 16 (shaded) are control signals, not power: Power on is to +5 V by the PSU, and must be driven low to turn on the PSU. is low when other outputs have not yet reached, or are about to leave, correct voltages. Pin 13 supplies +3.3 V power and also has a second thinner wire for . Pin 20 (formerly −5 V, white wire) is absent in current power supplies; it was optional in ATX and ATX12V ver. 1.2, and deleted as of ver. 1.3. The right-hand pins are numbered 11–20 in the 20-pin version.

Supply [V]	Tolerance	Range (min. to max.)	Ripple (p. to p. max.)
+5 V_DC	±5% (±0.25 V)	+4.75 V to +5.25 V	50 mV
−5 V_DC	±10% (±0.50 V)	–4.50 V to –5.50 V	50 mV
+12 V_DC	±5% (±0.60 V)	+11.40 V to +12.60 V	120 mV
−12 V_DC	±10% (±1.20 V)	–10.80 V to –13.20 V	120 mV
+3.3 V_DC	±5% (±0.165 V)	+3.135 V to +3.465 V	50 mV
+5 V_SB	±5% (±0.25 V)	+4.75 V to +5.25 V	50 mV

Physical characteristics[]

ATX power supplies generally have the dimensions of 150 × 86 × 140 mm (5.9 × 3.4 × 5.5 in)^:23–24 and share a common mounting layout of four screws arranged on the back side of the unit. That last dimension, the 140 mm depth, is frequently varied, with depths of 160, 180, 200 and 230 mm used to accommodate higher power or modular connectors.

Main changes from AT design[]

Power switch[]

AT-style computer cases had a power button that was directly connected to the system (PSU). The general configuration was a double-pole latching mains voltage switch with the four pins connected to wires from a four-core cable. The wires were either to the power button (making it difficult to replace the power supply if it failed) or were used.

Typical ATX 1.3 . From left to right, the connectors are 20-pin motherboard, 4-pin "P4 connector", fan RPM monitor (note the lack of a power wire), SATA power connector (black), "Molex connector" and floppy connector.

Interior view in an ATX power supply.

An ATX power supply is typically controlled by an electronic switch connected to the power button on the computer case and allows the computer to be turned off by the . In addition, many ATX power supplies have an equivalent-function manual switch on the back that also ensures no power is being sent to the components. When the switch on the power supply is turned off, however, the computer cannot be turned on with the front power button.

Power connection to the motherboard[]

The power supply's connection to the motherboard was changed from the older AT standard; ATs had two similar connectors that could be accidentally interchanged by forcing the different keyed connectors into place, usually causing short-circuits and irreversible damage to the motherboard (the rule of thumb for safe operation was to connect the side-by-side connectors with the black wires together). ATX used one large, keyed connector which could not be connected incorrectly. The new connector also provides a 3.3 volt source, removing the need for motherboards to derive this voltage from the 5 V rail. Some motherboards, particularly those manufactured after the introduction of ATX but while AT equipment was still in use, supported both AT and ATX PSUs.

If using an ATX PSU for other purposes than powering an ATX motherboard, power can be fully turned on (it is always partly on to operate "wake-up" devices) by shorting the "power-on" pin on the ATX connector (pin 16, green wire) to a black wire (ground), which is what the power button on an ATX system does. At least the specified minimum load required by the PSU should be present; the standard does not specify operation without load and a conforming PSU may shut down, output incorrect voltages, or otherwise malfunction, but will not be hazardous or damaged.

Airflow[]

The original ATX specification called for a power supply to be located near to the CPU with the power supply fan drawing in cooling air from outside the chassis and directing it onto the processor. It was thought that in this configuration, cooling of the processor would be achievable without the need of an active heatsink. This recommendation was removed from later specifications; modern ATX power supplies usually exhaust air from the case.

ATX power supply revisions[]

Original ATX[]

ATX, introduced in late 1995, defined three types of power connectors:

4-pin "" — transferred directly from AT standard: +5 V and +12 V for hard disks, CD-ROMs, 5.25 inch floppy drives and other peripherals.

4-pin — transferred directly from AT standard: +5 V and +12 V for 3.5 inch floppy drives and other peripherals.

20-pin main motherboard connector — new to the ATX standard.

A supplemental 6-pin AUX connector providing additional 3.3 V and 5 V supplies to the motherboard, if needed. This was used to power the CPU in motherboards with CPU which required 3.3 volt and/or 5 volt rails and could not get enough power through the regular 20-pin .

The power distribution specification defined that most of the PSU's power should be provided on 5 V and 3.3 V rails, because most of the electronic components (CPU, RAM, chipset, PCI, AGP and ISA cards) used 5 V or 3.3 V for power supply. The 12 V rail was only used by fans and motors of peripheral devices (HDD, FDD, CD-ROM, etc.).

The original ATX power supply specification was little revised until 2000.

ATX12V 1.x[]

While designing the Pentium 4 platform in 1999/2000, the standard 20-pin ATX power connector was found insufficient to meet increasing power-line requirements; the standard was significantly revised into ATX12V 1.0 (ATX12V 1.x is sometimes inaccurately called ATX-P4). ATX12V 1.x was also adopted by AMD Athlon XP and Athlon 64 systems. However, some early model Athlon XP and MP boards (including some server boards) and later model lower-end motherboards do not have the 4-pin connector as described below.

ATX12V 1.0[]

The main changes and additions in ATX12V 1.0 (released in February 2000) were:

Increased the power on the 12 V rail (power on 5 V and 3.3 V rails remained mostly the same).

An extra 4-pin mini fit JR (Molex 39-01-2040), 12-volt connector to power the CPU.

Formally called the +12 V Power Connector, this is commonly referred to as the P4 connector because this was first needed to support the processor.

Before the Pentium 4, processors were generally powered from the 5 V rail. Later processors operate at much lower voltages, typically around 1 V and some draw over 100 A. It is infeasible to provide power at such low voltages and high currents from a standard system power supply, so the Pentium 4 established the practice of generating it with a on the motherboard next to the processor, powered by the 4-pin 12 V connector.

ATX12V 1.1[]

This is a minor revision from August 2000. The power on the 3.3 V rail was slightly increased and other smaller changes were made. atx has 12 pin and 12 volt

ATX12V 1.2[]

A relatively minor revision from January 2002. The only significant change was that the −5 V rail was no longer required (it became optional). This voltage was used only on some old systems with certain ISA add-on cards.

ATX12V 1.3[]

Introduced in April 2003 (a month after 2.0). This standard introduced some changes, mostly minor. Some of them are:

Slightly increased the power on 12 V rail.

Defined minimal required PSU efficiencies for light and normal load.

Defined acoustic levels.

Introduction of Serial ATA power connector (but defined as optional).

Guidance for the −5 V rail was removed (but it was not prohibited).

ATX12V 2.x[]

ATX12V 2.x brought a very significant design change regarding power distribution. On analyzing the then-current PC architecture's power demands, it was determined that it would be much cheaper and more practical to power most PC components from 12 V rails, instead of from 3.3 V and 5 V rails.

ATX12V 2.0[]

ATX-450PNF by FSP Group

The above conclusion was incorporated in ATX12V 2.0 (introduced in February 2003), which defined quite different power distribution from ATX12V 1.x:

Most power is now provided on 12 V rails. The standard specifies that two independent 12 V rails (12 V₂ for the 4 pin connector and 12 V₁ for everything else) with independent overcurrent protection are needed to meet the power requirements safely (some very high power PSUs have more than two rails, recommendations for such large PSUs are not given by the standard).

The power on 3.3 V and 5 V rails was significantly reduced.

The main ATX power connector was extended to 24 pins. The extra four pins provide one additional 3.3 V, 5 V and 12 V circuit.

The 6-pin AUX connector from ATX12V 1.x was removed because the extra 3.3 V and 5 V circuits which it provided are now incorporated in the 24-pin main connector.

The power supply is required to include a .

Many other specification changes and additions

ATX12V v2.01[]

This is a minor revision from June 2004. An errant reference for the −5 V rail was removed. Other minor changes were introduced.

ATX12V v2.1[]

This is a minor revision from March 2005. The power was slightly increased on all rails. Efficiency requirements changed.

ATX12V v2.2[]

Another minor revision.

Specified High Current Series wire terminals for 24-pin main and 4-pin +12 V power connectors.

ATX12V v2.3[]

Effective March 2007 and current as of 2012. Recommended efficiency was increased to 80% (with at least 70% required) and the 12 V minimum load requirement was lowered. Higher efficiency generally results in less power consumption (and less waste heat) and the 80% recommendation brings supplies in line with new mandates. The reduced load requirement allows compatibility with processors that draw very little power during startup. The absolute over-current limit of 240 VA per rail was removed, allowing 12 V lines to provide more than 20 A per rail.

ATX power supply derivatives[]

SFX[]

SFX is merely a form factor for a power supply casing and the power specifications are almost identical. Thus, an SFX power supply is mostly interchangeable with the ATX power supply. The only difference is that the SFX specifications do not require the −5 V rail. Since −5 V is required only by some ISA bus expansion cards, this is not an issue with modern hardware and decreases productions costs. As a result, ATX pin 20, which carried −5 V, is absent in current power supplies; it was optional in ATX and ATX12V version 1.2 and deleted as of version 1.3.

SFX has dimensions of 100×125×63.5 mm (width×depth×height) with 60 mm fan. Optional 80 or 40 mm fan replacement increases or decreases the height of the unit.

Some manufacturers and retailers incorrectly market SFX power supplies as µATX or MicroATX power supplies.

TFX[]

Another small form factor power supply with standard ATX specification connectors. Generally 5.75×3.25×2.5 in (D) × (W) × (H) (146×83×64 mm).

WTX[]

Provides a style motherboard connector which is incompatible with the standard ATX motherboard connector.

AMD GES[]

This is an ATX12V power supply derivative made by AMD to power its Athlon MP (dual processor) platform. It was used only on high-end Athlon MP motherboards. It has a special 8-pin supplemental connector for motherboard, so an AMD GES PSU is required for such motherboards (those motherboards will not work with ATX(12 V) PSUs).

EPS12V[]

is defined in and used primarily by /multi-core systems such as , , and . It has a 24-pin main connector (same as ATX12V v2.x), an 8-pin secondary connector and an optional 4-pin tertiary connector. Rather than include the extra cable, many power supply makers implement the 8-pin connector as two combinable 4-pin connectors to ensure backwards compatibility with ATX12V motherboards.

Recent specification changes and additions[]

High-performance video card power demands dramatically increased during the 2000s and some high-end graphics cards have power demands that exceed or slot capabilities. For these cards, supplementary power was delivered through a standard 4-pin peripheral or floppy power connector. Midrange and high-end PCIe graphics cards manufactured after 2004 typically use a standard 6 or 8-pin PCIe power connector directly from the PSU.

Interchanging PSUs[]

Although the ATX power supply specifications are mostly vertically compatible in both ways (both electrically and physically), there are potential issues with mixing old motherboards/systems with new PSUs and vice versa. The main issues to consider are the following:

The power allocation between 3.3 V, 5 V and 12 V are very different between older and newer ATX PSU designs, as well as between older and newer PC system designs.

Older PSUs may not have connectors which are required for newer PC systems to properly operate.

Newer systems generally have higher power requirements than older systems.

This is a practical guidance what to mix and what not to mix:

Older systems (before Pentium 4 and Athlon XP platforms) were designed to draw most power from 5 V and 3.3 V rails.

Because of the DC-DC converters on the motherboard that convert 12 V to the low voltages required by the Intel Pentium 4 and AMD Athlon XP (and subsequent) processors, such systems draw most of their power from the 12 V rail.

Original ATX PSUs have power distribution designed for pre-P4/XP PCs. They lack the supplemental 4-pin 12-volt CPU power connector, so they most likely cannot be used with P4/XP or newer motherboards. Adapters do exist but power drain on the 12 V rail must be checked very carefully. There is a chance it can work without connecting the 4-pin 12 V connector, but caution is advised.^[]

ATX12V 1.x PSUs have power distribution designed for P4/XP PCs, but they are also greatly suitable for older PCs, since they give plenty of power (relative to old PCs' needs) both on 12 V and on 5 V/3.3 V. It is not recommended to use ATX12V 1.x PSUs on ATX12V 2.x motherboards because those systems require much more power on 12 V and much less on 3.3 V/5 V than ATX12V 1.x PSUs provide.

ATX12V 2.x PSUs have power distribution designed for late P4/XP PCs and for Athlon 64 and Core Duo PCs. They can be used with earlier P4/XP PCs, but the power distribution will be significantly suboptimal, so a more powerful ATX12V 2.0 PSU should be used to compensate for that discrepancy. ATX12V 2.x PSUs can also be used with pre-P4/XP systems, but the power distribution will be greatly suboptimal (12 V rails will be mostly unused, while the 3.3 V/5 V rails will be overloaded), so this is not recommended.

Systems that use an ISA bus should have a PSU that provides the −5 V rail, which became optional in ATX12V 1.2 and was subsequently phased out by manufacturers.

Not all computers use standard, interchangeable ATX power supplies. In particular, some proprietary brand-name machines and high-end workstation and server designs do not and require an exactly matching power supply unit.

ATX[]

维基百科，自由的百科全书

提示：本条目的主题不是

。



规格	尺寸 (mm)
	356×425
	350×305
	330×216
	325×266
ATX	305×244
	305×330
	330×229
	254×228
	244×244
	244×203
	229×191
	203×170
	203×146
	171×171
	170×170
	165×115
	149×71
	120×120
	125×95
	125×95
	114×95
	100×72
	96×90
	75×45
	?×244

ATX（Advanced Technology Extended）由公司在制定。这是多年来第一次电脑机壳与主板设计的重大改变。ATX取代了主板规格，成为较新电脑系统默认的主板规格。ATX解决了以往中，令电脑组装人士烦恼的问题。其他派生的主板规格（包括、与）保留了ATX基本的背板设置，但主板的面积减少，扩充槽的数目也有所删减。

自英特尔在1995年发表最初的ATX官方规格后，此规格经历多次变更；最新2.3版本规格于2007年发表。标准的ATX主机版，长12英吋，宽9.6英吋（305毫米 x 244毫米）。这也容许标准的ATX机箱容纳较小的microATX主板。

，英特尔发布全新的主板规格，以其作为ATX的替代规格。但由于兼容性的问题，ATX规格仍为组装电脑最通行的主板规格，只有大型厂商的零售电脑采用BTX，因此英特尔于2006年起放弃BTX的发展。

电源供应器[]

由于ATX主板比起较旧的AT主板有更多优点，因此广为现代电脑系统采用。

典型的ATX电源供应器。

过往的AT电脑机箱，具有一个直接连到电源供应器的电源开关。开关的主要形式，是一个双极式的开关，开关的四条针脚，连到对应的电线。由于电线是到电源开关，因此，如果电源供应器损坏，更换就会变得非常困难。

ATX的电源供应器，并不直接连到电脑的电源开关，因此电脑可以通过。不过，大多数的ATX电源供应器，背面具有一个手动开关，容许用户将电脑完全关闭；电脑在此时将不会得到任何电力。当这个开关打开的时候，就算表面上电脑已经“关机”，电力仍然会进入电脑各部件。这种“软件关机”或“待命”的特征，可以用于遥控开机（例如通过开机，即，或通过，即），但一般而言，电脑仍然是通过前面的开关来开机。

ATX电源供应器连到主板的插头，比起AT也有所变更。旧式的AT电源供应器，使用两个形状相似的插头连到主板，由于易于错接，主板很容易会因为短路而受到永久损坏。ATX则使用一个具方向性的插头，反方向时不能插入主板，此免除损坏主板的风险。另外，ATX也提供一个3.3伏特的电源，主板因此无须再使用其他的电源来“间接降压”取得3.3伏特电源。一些最后期生产的AT主板，也同时支持AT与ATX的电源供应器。

另外，原来的ATX设计，是利用电源供应器的风扇，将空气抽进机箱内，为主板与处理器提供散热用的空气气流。因为这个缘故，处理器一般是放于主板的上方。由于众多原因，这个设计对于机箱的散热没有多大用处。首先，早期的处理器与组件，发出的热量并不需要使用特别的散热设备进行散热。其后的处理器发热量增多，但电源供应器吹出来的空气已经明显较热，令这种散热方式变为无用。因此，较后的ATX规格已经将电源供应器的气流设计，变为选用设计。

其后Intel的出现，标准的20针ATX电源接脚开始无法提供处理器需要的较大电量，因此，新的ATX规格再加上了一个4针的12伏特电源接头。这个设计也用于AMD的与处理器。一些高价系统，也适用其他形式的辅助电源接头。

到了，显卡的电量需求大幅上升，一些高价显卡的电量需求，更超越了与的供电能力，因此高价显卡也开始备有与硬盘驱动器电源类似的接头，以取得额外的电力。以后生产的PCI Express显卡，更开始使用一个标准的6针或8针接头，从电源供应器直接取电。

ATX电源供应器是通过主板的开关来操作，理论上，只要将ATX插头中的绿色电线接头（开关信号）与任何接头中的黑色电线（接地）连接，即可以在不使用主板的情况下打开电源。一些旧的电源供应器，可以用这种方式为电脑以外的设备供电，不过改装时，则需要留意电源供应器的最低负载需求。

标准[]

ATX[]

初版的ATX于1995年发表，定义了三种接头。

4-Pin Molex——用来连接、5.25吋及其他周边设备

4-Pin Berg floppy connector——用来连接3.5吋及其他周边设备

20-Pin Molex Mini-fit Jr.——用来连接

ATX12V 1.x[]

1999年，设计时发现原有的ATX标准不足提供足够的电力，于是发表了新的ATX12V（又称ATX-P4）。AMD亦采用此标准，用于Athlon XP及Athlon 64平台。

ATX12V 1.0

2000年2月发表

增加了12V的供电能力（3.3V和5V大致不变）

新增mini fit JR (Molex 39-01-2040)——4-Pin接头，额外提供12V供电到

ATX12V 1.1

2000年8月发表

增加了3.3V的供电能力

ATX12V 1.2

2002年1月发表的小修订

不再要求电源供应器提供-5V

ATX12V 2.x[]

ATX12V 2.x是一个重大的修订，电力供应主要由12V提供。

ATX12V 2.0

增加12V的供电能力，要求有两组12V回路，及独立的过电流保护

减低3.3V和5V的供电能力

主接头扩展到24-Pin，增加的四针分别是3.3V、5V、12V和

要求电线

ATX12V 2.1

2005年3月发表的小修订

增加各回路的供电能力

转换效率改变

ATX12V 2.2

ATX12V 2.3

2007年3月发表的小修订

移除12V单轨输出最多240VA的限制，即单轨12V可以输出超过20A

建议转换效率提升到80%，最低转换效率最少要有70%

戴尔电脑的电源供应器[]

早期的，尤其是使用Pentium II与Pentium III的型号，使用一种专属的电源接脚方式。外观上电源接头与标准的ATX类同（事实上也可以插进标准的电源供应器），接脚的定义却并不兼容；除了电线位置变更以外，使用某一电压的电线数目也有所变化，令针脚不能轻易再行变更与改装。

除了20针主接头以外，辅助的6针接头也受到影响。虽然较新的戴尔电脑，可能使用标准的ATX电源，但是将其他的主板与电源供应器用于戴尔电脑时就要相当小心，以免烧坏主板或电源供应器。基本上，如果电源供应器的电线颜色编码与ATX标准不同，那很大机会就会是专属的接线。一般来说，戴尔电脑的支持网站，会提供有关电源接线的数据与图解。

接头[]

ATX的输入／输出背板

ATX规格也于电脑的背板作出一些主要的变更。AT规格只有一个键盘的插座，与安装适配器使用的扩充槽。其他的接口，例如与，就需要通过接线，连到机箱预留的空间，或未使用的扩充槽后面的铁片。ATX则容许将这些接口，排列在主板后面一个特定的长方形区域，排列的方式可以由主板厂商自定义（不过大部分的主板厂商，使用一些广为接受的排列方式）。基本上，机箱后面有一块可以拆下的铁片，称为“输入／输出背板”，开孔的形式与主板上的接口对应。这块输入／输出背板，可以因应不同的主板而加以替换，事实上，市售的主板也包括一块对应的输入／输出背板。此外，也有一些特别设计的背板，容许旧式的AT主板，安装到ATX机箱中。

ATX的出现，也统一了mini-DIN键盘与PS/2鼠标插座的使用。相比之下，AT系统使用一个5针DIN接头连接键盘，并搭配串行端口鼠标一同使用（不过也有部份AT电脑使用PS/2鼠标）。

大小[]

发表年份	标准	宽度	深度
1995	ATX	12 in (305 mm)	9.6 in (244 mm)
1995	EATX (Extended ATX)	12 in (305 mm)	13 in (330 mm)
1996	Mini ATX	11.2 in (284 mm)	8.2 in (208 mm)
1997	与 EmbATX	9.6 in (244 mm)	9.6 in (244 mm)
1998	(Workstation ATX)	14 in (356 mm)	16.75 in (425 mm)
1999		9 in (229 mm)	7.5 in (191 mm)
	EEATX (Enhanced Extended ATX)	13.68 in (347 mm)	13 in (330 mm)

1995年制定的EATX标准为12×13寸，主要用于双路处理器平台，即一块主板有两个CPU。

现在一些生产商的EATX主板并不是长13寸，这些主板宽度维持12寸，长度每一间公司都不同，通常是10到11寸。这些主板都通常是顶级的单路处理器平台，因为ATX太小无法放入所有组件，而改用“EATX”。

参见[]

Mini-ITX

From Wikipedia, the free encyclopedia


Listed by size (mm)
Mini-ITX (170×170)

A VIA mini-ITX motherboard

Mini-ITX is a 17 × 17 cm (6.7 × 6.7 in) low-power developed by in 2001.They are commonly used in computer systems. Mini-ITX boards can often be passively cooled due to their low , which makes them useful for systems, where fan noise can detract from the cinema experience. The four mounting holes in a Mini-ITX board line up with four of the holes in ATX-specification motherboards, and the locations of the backplate and are the same (though one of the holes used was optional in earlier versions of the ATX spec). Mini-ITX boards can therefore often be used in cases designed for ATX, micro-ATX and other ATX variants if desired.

The form factor has provision for one expansion slot, conventionally a standard 33 MHz 5V 32-bit slot. Many case designs use riser cards and some even have two-slot riser cards, although the two-slot riser cards are not compatible with all boards. Some boards based around non-x86 processors have a 3.3V PCI slot, and the Mini-ITX 2.0 (2008) boards have a PCI-express ×16 slot; these boards are not compatible with the standard PCI riser cards supplied with cases.

[]

History[]

ITX motherboard form factor comparison

In March 2001, the manufacturer released a reference design for an ITX motherboard, to promote the low power they had bought from , in combination with their chipsets. Designed by Robert Kuo, VIA's chief R&D expert, the 215×191 mm VT6009 ITX Reference Board was demonstrated in "Information PC" and form factors. He would later go on to design the Mini-ITX form factor. The ITX form factor was never taken up by manufacturers, who instead produced smaller boards based on the very similar 229×191 mm FlexATX form factor.

In October 2001, VIA announced their decision to create a new motherboard division, to provide standardized infrastructure for lower-cost PC form factors and focus on . The result was the November 2001 release of the VT6010 Mini-ITX reference design, once again touted as an "Information PC", or low cost entry level computing platform. Manufacturers were still reticent, but customer response was much more receptive, so VIA decided to manufacture and sell the boards themselves. In April 2002 the first Mini-ITX motherboards—VIA's 5000 (fanless 533 MHz Eden processor) and EPIA 800 (800 MHz C3)—were sold to industrial customers.

Enthusiasts soon noticed the advantages of small size, low noise and power consumption, and started to push the boundaries of into something else—building computers into nearly every object imaginable, and sometimes even creating new cases altogether. Hollowed out vintage computers, , ,, , and even a 1960s-era have become homes to relatively quiet, or even silent Mini-ITX systems, capable of many of the tasks of a modern desktop .

Mini-ITX boards primarily appeal to the industrial and embedded PC markets, with the majority sold as bulk components or integrated into a finished system for single-purpose computing applications. They are produced with a much longer sales life-cycle than consumer boards (some of the original are still available), a quality that industrial users typically require. Manufacturers can prototype using standard cases and power supplies, then build their own enclosures if volumes get high enough. Typical applications include playing music in , powering self-service kiosks, and driving content on digital displays.

VIA has continued to expand its Mini-ITX motherboard line. Some of the earlier generations included the original PL133 chipset boards (dubbed the "Classic" boards), CLE266 chipset boards (adding MPEG-2 acceleration), and CN400 boards (which added acceleration). Second generation boards featured the EPIA M, MII, CL, PD, TC and MS — all tailored to slightly different markets. Legacy VIA boards use their x86-compatible CPUs — the C3, C7 or low-power Eden variants, with newer boards featuring the VIA Nano CPU, launched in May 2008. Other manufacturers have also produced boards designed around the same form factor, using VIA, but also , , and technology.

has introduced a line of Mini-ITX boards for the , which demonstrates a significant increase in processing performance (but without added power consumption) over older VIA C3 and C7 offerings and is key to making the form factor viable for use in personal computers. Other manufacturers saw the potential of the form factor and followed suit, some even not limiting themselves to the Atom, as evidenced by GeForce 9300-ITX board that supports CPUs with frequencies up to 1333 MHz, two separate-channeled 800 MHz memory slots and fully functional x16 slot that could connect through to the onboard video. This new wave of offerings has caused Mini-ITX to explode in popularity among home users, hobbyists and even overclockers.

is currently one of very few manufacturers of Mini-ITX mainboards that also include the mechanical dimensions in their manuals.

Consumer product[]

Since VIA focuses on IPC, their Mini-ITX products were designed and sold to the industrial and system integrator markets. is the primary early provider that designed and marketed Mini-ITX motherboards to the consumer market in 2006.

Intel-based products[]

The first AOpen Mini-ITX motherboard was the i945GTt-VFA, it supports 667 MHz FSB Intel Core Duo/Core Solo Socket 479 CPU and Intel Viiv technology for setting up an HTPC (Home Theater PC). The latest AOpen Mini-ITX motherboard is nMCP7ASt-V that adapts Socket 775 Intel Core 2 Quad/Core 2 Duo/Celeron FSB 533/800/1066/1333 MHz CPU, Dual Channel DDR2 667/800 MHz SDRAM up to 4GB, and a PCI Express x 16 Slot (Support nVIDIA Hybrid SLI technology and PCI Express 2.0 via nVIDIA MCP7A-S chipset).

Some time ago, GIGABYTE Technology announced a mini-ITX P55 based motherboard. The board features the LGA-1156 socket with support for Core i3/i5/i7 CPUs. It includes two DDR3 memory slots and a single PCI-Express ×16 slot, which is required due to the lack of integrated graphics. For connections it has eSATA and four SATA II ports, eight USB 2.0, two USB 3.0, a Gigabit LAN and 8 channel audio with SPDIF.

There are many contemporary LGA1155 mainboards for and CPUs in Mini-ITX form-factor on the market now. A typical Mini-ITX LGA1155 mainboard not only allows for integrated graphics, but can also take an external graphics accelerator. That is why there is often a PCI Express 2.0 x16 slot. Moreover, many mainboard makers provide their products with additional mini-PCI Express slots that can be used for extra expansion cards, such as Wi-Fi, TV-tuner cards, SSD, etc. SATA 6 Gbit/s and USB 3.0 are often supported on the original versions of these mainboards, which is why Mini-ITX LGA1155 mainboards can be high-performance / up-to-date platforms.

AMD-based product[]

Alix.1C Mini-ITX embedded board with LX 800 together with , and PCI slots, 44-pin interface and 256MB RAM

AOpen also made the first based Mini-ITX motherboard, the MCP68PVNt-HD, it supports and for home theater PC systems and comes with the MCP68PVNT chipset for AMD Athlon 64 X2, Athlon 64, and Sempron CPU with AM2 socket. The MCP68PVNT supports DirectX 9 and the hardware decoding decreases the CPU load when playing HD content. AOpen nMCP68PVNt-HD has a HDMI port that support 480P, 720P and 1080P high-definition video and audio with HDCP.

Power[]

The Mini-ITX standard does not define a standard for the power supply, though it makes some suggestions of possible options. Conventionally Mini-ITX boards use a 20- or 24-pin "original ATX" power connector. This is usually connected to a DC-DC converter board which in turn is connected to an external power adapter. Generally both the power adapter and the DC-DC board are supplied with the case.

Some boards have built in DC-DC converters and converters have also been made to plug directly into the ATX connector (e.g. the ), either of these options avoids the need to mount a separate DC-DC converter into the case, saving space and design effort. Boards using full-power Intel or AMD CPUs typically use ATX12V 2.x connections and require a case with appropriate power supply and cooling for these more power-hungry chips.

Mini-ITX[]

维基百科，自由的百科全书



规格	尺寸 (mm)
	356×425
	350×305
	330×216
	325×266
	305×244
	305×330
	330×229
	254×228
	244×244
	244×203
	229×191
	203×170
	203×146
	171×171
Mini-ITX	170×170
	165×115
	149×71
	120×120
	125×95
	125×95
	114×95
	100×72
	96×90
	75×45
	?×244