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2024年2月21日发(作者：秘豪)

Mini-ITX Addendum Version 2.0

To the microATX Motherboard

Interface Specification Version 1.2

October 2010

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Contents

Revision History ..................................................................................................................... 4

Executive Summary ........................................................................................... 5

1.1

1.2

1.3

1.4

2.1

2.2

2.3

2.4

Terminology ........................................................................................... 6

Reference Documents .............................................................................. 6

Benefits to Users .................................................................................... 6

Benefits to Manufacturers ........................................................................ 6

Board Dimensions ................................................................................... 9

Mounting Hole Placement ......................................................................... 9

Connector Placement .............................................................................. 11

2.3.1

Thin Mini-ITX Back Panel I/O ...................................................... 11

Height Constraints ................................................................................. 11

2.4.1

Mini-ITX: Primary (Component) Side Height Constraints ................ 11

2.4.2

Thin Mini-ITX: Primary (Component) Side Height Constraints ......... 12

2.4.3

Secondary (Bottom/Solder) Side Height Constraints ..................... 14

2.4.4

Thin Mini-ITX System Considerations .......................................... 14

Layout .............................................................................................................. 8

Power Supply Information .................................................................................. 16

Figures

Figure 1. Example Mini-ITX Layout for SFF Desktop .............................................. 8

Figure 2. ATX, microATX, and Mini-ITX 9

Figure 3. Mini-ITX Board Diagram ...................................................................... 10

Figure 4. Thin Mini-ITX Back Panel I/O ............................................................... 11

Figure 5. Mini-ITX Maximum Component Height Restrictions ................................. 12

Figure 6. Thin Mini-ITX Maximum Component Height Restrictions .......................... 14

Tables

Table 1. Mini-ITX Addendum Feature Summary .................................................... 5

Table 2. Compares ATX, microATX, and Mini-ITX Board Dimensions ........................ 9

Table 3. Motherboard Mounting Hole Locations .................................................... 10

Revision History

Revision

Number

2.0

Description

Added Thin Mini-ITX definition.

Revision Date

Oct, 2010

1.1 Minor corrections made. Title changed to:

‘Mini-ITX Addendum Version 1.1 To the microATX

Motherboard Interface Specification Version 1.2’

to reflect full name of mATX document name.

Feb, 2009

1.0 Initial release. Feb, 2009

1 Executive Summary

The Mini-ITX addendum to the microATX Motherboard Interface Specification details

the use the Mini-ITX form factor standard, developed by Via Technologies Inc, for

compatibility with Intel based platforms. This document defines only the specific

features in Intel’s Mini-ITX based platforms that differ from those of microATX and

should be used in conjunction with the governing microATX specification.

A smaller motherboard layout offers system developers the ability to create new and

innovative system designs. This smaller version of microATX allows and encourages

developers to build within the sub 8 liter chassis volume for a variety of new

applications.

Described within this document are requirements and characteristics of a Mini-ITX

motherboard, so that a motherboard may function and fit appropriately when paired

with a Mini-ITX chassis. Beyond this, it does not detail processor, memory, graphics

or other system features required to meet the Mini-ITX form factor. These items are

left to system designers and integrators within the guidelines of the microATX

specification.

A further refinement of Mini-ITX boards is the Thin Mini-ITX board definition. Its

smaller size enables system integrators to integrate sub-4 liter systems, such as Tiny

PCs and All-In-One PCs, using a standard building block approach.

Table 1. Mini-ITX Addendum Feature Summary

Feature

170mm x 170mm motherboard size

Mini-ITX: Standard microATX 1.2 or later I/O

panel

Thin Mini-ITX: A Mini-ITX board targeted for

smaller system form factors with a 20mm tall

PCB and component volumetric, and a 1” back

panel I/O height

Same motherboard mounting holes as in

microATX

Current processor and future processor

technologies

Benefit

Smaller board size enables a smaller system

size.

ATX I/O shield does not need to be retooled.

Motherboard can be used in an ATX, microATX,

or Mini-ITX chassis.

A Thin Mini-ITX board can use a thin back

panel I/O shield when targeted for Tiny PCs

and AIOs. The same board can be used in a

Mini-ITX, microATX, and ATX chassis when

used with a regular ATX I/O shield.

Compatible with microATX chassis. No need to

retool current chassis.

Chassis will work for multi generation socketed

processor technology.

This addendum does NOT define:



Specific power supply form factors

Thermal design guidance to chassis vendors (covered in TASC guide listed in

Reference Documents)

The Mini-ITX Addendum To the microATX Motherboard Interface Specification is a

public document intended for widespread application in many types of systems. It is

available through a public website located at:

1.1 Terminology

Term

Small Form Factor (SFF)

Ultra SFF (uSFF)

Tiny PC

All-In-One (AIO) PC

Description

8-19 liter chassis (IDC* definition)

4-8 liter chassis (IDC* definition)

Less than 4 liter chassis (IDC* definition)

An All-In-One is a desktop PC with a display built into the main

computing unit (IDC* definition)

1.2 Reference Documents

The following reference documents are posted on the public web site at:

Document

microATX Motherboard Interface Specification Version 1.2

SFX 12V Power Supply Design Guide

TFX 12V Power Supply Design Guide

Thermally Advantaged Small Chassis or TASC [pronounced ‘task’] (Thermal Design Guide)

1.3 Benefits to Users

Trends in the industry indicate that users require a smaller and lower cost solution for

their PC needs. Mini-ITX’s smaller board size and lower height keep-out zones enable

a reduced sized chassis as it sits on the user’s desk, is mounted on a display, or

comes in any other innovative form factor. These changes also enable a PC to be

designed into various aesthetic shapes and sizes. The Thin Mini-ITX board variation

leverages Mini-ITX’s advantages, while enabling even thinner systems.

1.4 Benefits to Manufacturers

By manufacturing to the standard or thin variations of the Mini-ITX specification,

motherboard manufacturers and chassis manufacturers can guarantee a better

compatibility between their products. They can also capitalize on the benefits of a

reduction in total system costs because of a reduced system size. This specification

allows chassis vendors to design their product targeting the soldered down, low power

processors all the way up to high performance, multi-core processors. It eliminates

the need for them to design targeted chassis for each platform.

2 Layout

This section describes the mechanical specifications of the Mini-ITX and Thin Mini-ITX

form-factor motherboards. Size, mounting hole placement, connector placement, and

component height constraints are specified. System components such as hard drives,

disk drives, and power supplies are not specified; however, it is generally

recommended to consider what would facilitate assembly, as well as not place

components such that they block fan inlets. An example layout is depicted in Figure

Thin Mini-ITX is a variant of standard Mini-ITX and shares most of the same

requirements. Requirements are only different where new specifications are

specifically defined for Thin Mini-ITX.

Figure 1. Example Mini-ITX Layout for SFF Desktop

NOTE: Depicted system is approximately 8L with standard desktop components.

2.1 Board Dimensions

Dimension

Maximum width Allowable

Maximum depth Allowable

ATX

305mm

244mm

microATX

244mm

Mini-ITX

170mm

Table 2. Compares ATX, microATX, and Mini-ITX Board Dimensions

2.2 Mounting Hole Placement

Mini-ITX utilizes a subset of ATX mounting holes. To avoid damage to traces on

motherboards, chassis standoffs in any locations not specified should be removable or

not implemented at all. See Figure 2 for relative hole locations compared to ATX and

microATX motherboards.

Figure 2. ATX, microATX, and Mini-ITX Mounting Holes

NOTE: Board is shown oriented with the rear of the board towards the top.

NOTE: The lighter portion indicates the approximate region of the Mini-ITX form factor.

Table 3. Motherboard Mounting Hole Locations

Form Factor

Mini-ITX

microATX

ATX

Mounting Hole Locations

C,F,H,J

B,C,F,H,J,L,M,R,S

A,C,F,G,H,J,K,L,M

Figure 3. Mini-ITX Board Diagram

2.3 Connector Placement

For Mini-ITX, all connector locations as well as allowable placement area for I/O

connectors on the back panel are described and can be found in the microATX

Interface Specification.

2.3.1 Thin Mini-ITX Back Panel I/O

The Thin Mini-ITX Back Panel I/O area is defined in Figure 4. The width of the back

panel I/O aperture and the location of the motherboard relative to the I/O aperture

are the same as Mini-ITX. This allows a Thin Mini-ITX board to be used in either a

Thin Mini-ITX chassis, or a Mini-ITX and larger compatible chassis when using an

appropriate I/O shield.

The thickness of the PCB and the topside I/O connectors shall fit within the .787”

(20mm) height shown in Figure 4. See section 2.4.2 for additional discussion.

Figure 4. Thin Mini-ITX Back Panel I/O

2.4

2.4.1

Height Constraints

Mini-ITX: Primary (Component) Side Height Constraints

One major advantages of the Mini-ITX form factor is its backward-compatibility with

the ATX specification. The Mini-ITX motherboard can be installed in any ATX chassis.

Figure 5 shows the required Mini-ITX maximum component height constraints for

the components on the PC board. For full compliance with Mini-ITX, and to prevent

interference with the chassis structure, power supply, or peripherals, the motherboard

components should not exceed the height limit in each zone defined. Similarly,

compliant power supplies, peripherals, and chassis features should not extend into the

motherboard component area.

Figure 5. Mini-ITX Maximum Component Height Restrictions

Notes:



All dimensions in the above figure are in millimeters (mm).

The 57mm height restriction in Area A applies to the PC board component height.

The actual height of the chassis should include any dynamic excursion

considerations for shipping as well as needs to facilitate alternative cooling

solutions or airflow considerations.

For the Intel boxed processor fan heat sink, it is strongly recommended not to

place components between fan inlet and chassis side vent by leaving space

between chassis wall and area A open.

The component height requirement assumes a motherboard thickness of 1.57 mm

(.062”).



2.4.2 Thin Mini-ITX: Primary (Component) Side Height

Constraints

Figure 6 shows the required Thin Mini-ITX volumetric envelope for the PCB and all

motherboard components. For full compliance with Thin Mini-ITX, and to prevent

interference with the chassis structure and other system components, the

motherboard components must not exceed the height limit in each zone defined.

In Area A, the thickness of the PCB and the topside components shall fit within the

.787” (20mm) height shown in Figure 6. With this in mind, motherboard designers

may exercise tradeoffs between board thickness and the height of I/O components as

necessary. For example, a .062” (1.57mm) PCB would allow .725” (18.43mm) for

topside components, while a .093” (2.36mm) PCB would allow .694” (17.64mm).

Chassis features and system components must not extend into the motherboard

component area. Additionally, space must be permitted around the motherboard by

the chassis and other system components to allow for dynamic excursion

considerations, as well as needs to facilitate alternative cooling solutions or airflow

considerations.

Depending on the needs of the system, components that interface with the

motherboard but are not part of it, such as a CPU heatsink, may fit within the

volumetric established in Figure 6 or extend outside of it. Any components that

extend through the motherboard volumetric must be selected in cooperation with the

chassis to ensure there are no interference issues. The motherboard may have its

own specific keep-in or keep-out requirements, such as around a CPU for its heatsink,

which may also need to be considered.

Figure 6. Thin Mini-ITX Maximum Component Height Restrictions

2.4.3 Secondary (Bottom/Solder) Side Height Constraints

No height restraints on secondary side are added or removed from what is specified in

the microATX Motherboard Interface Specification.

2.4.4 Thin Mini-ITX System Considerations

While the low profile design of a Thin Mini-ITX motherboard creates the opportunity

for smaller PCs, system space must be allowed for factors such as airflow and cabling.

Board headers and the cable connectors they mate to should be selected with size and

orientation in mind. The use of tall headers which are perpendicular to the

motherboard and/or long cable connectors increase the chance of interference with

chassis components immediately over a Thin Mini-ITX board.

System integration challenges can be addressed in a variety of ways, including:



Carefully considering venting and fan/blower strategies to ensure proper cooling

can be achieved in a small chassis.

Minimizing the size of board headers and cable connectors.

Using board headers which are parallel or angled to the PCB, provided sufficient

space around and/or on the board is included in the system design for proper

cable mating and connector space.

3 Power Supply Information

Provided the very different needs of the platforms that fit in the small desktop form

category, this specification does not attempt to define a standard for the power supply

to match with the Mini-ITX motherboard specification. Instead it recommends that

manufacturers consider using a:



SFX, TFX or FlexATX* are available power supply form factor for chassis greater

than 4 liters.

External power adapter for chassis less than 4 liters and All-in-One desktop

PCs.**

* Refer to the microATX Motherboard Interface Specification for information on power

supply requirements.

** Refer to related system design guides for information on AIO power supply

requirements.