Balanced Technology Extended (BTX) Interface Specification v1.0a.pdf · Balanced Technology...

Balanced Technology Extended (BTX) Interface Specification

Version 1.0a

Balanced Technology Extended (BTX) Interface Specification Version 1.0a

IMPORTANT INFORMATION AND DISCLAIMERS

1. INTEL CORPORATION MAKES NO WARRANTIES WITH REGARD TO THIS BALANCED TECHNOLOGY EXTENDED (BTX) SPECIFICATION (“SPECIFICATION”), AND IN PARTICULAR DOES NOT WARRANT OR REPRESENT THAT THIS SPECIFICATION OR ANY PRODUCTS MADE IN CONFORMANCE WITH IT WILL WORK IN THE INTENDED MANNER. NOR DOES INTEL ASSUME RESPONSIBILITY FOR ANY ERRORS THAT THE SPECIFICATION MAY CONTAIN OR HAVE ANY LIABILITIES OR OBLIGATIONS FOR DAMAGES INCLUDING, BUT NOT LIMITED TO, SPECIAL, INCIDENTAL, INDIRECT, PUNITIVE, OR CONSEQUENTIAL DAMAGES WHETHER ARISING FROM OR IN CONNECTION WITH THE USE OF THIS SPECIFICATION IN ANY WAY.

2. NO REPRESENTATIONS OR WARRANTIES ARE MADE THAT ANY PRODUCT BASED IN WHOLE OR IN PART ON THE ABOVE SPECIFICATION WILL BE FREE FROM DEFECTS OR SAFE FOR USE FOR ITS INTENDED PURPOSE. ANY PERSON MAKING, USING OR SELLING SUCH PRODUCT DOES SO AT HIS OR HER OWN RISK.

3. THE USER OF THIS SPECIFICATION HEREBY EXPRESSLY ACKNOWLEDGES THAT THE SPECIFICATION IS PROVIDED AS IS, AND THAT INTEL CORPORATION MAKES NO REPRESENTATIONS, EXTENDS NO WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, ORAL OR WRITTEN, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, OR WARRANTY OR REPRESENTATION THAT THE SPECIFICATION OR ANY PRODUCT OR TECHNOLOGY UTILIZING THE SPECIFICATION OR ANY SUBSET OF THE SPECIFICATION WILL BE FREE FROM ANY CLAIMS OF INFRINGEMENT OF ANY INTELLECTUAL PROPERTY, INCLUDING PATENTS, COPYRIGHT AND TRADE SECRETS NOR DOES INTEL ASSUME ANY OTHER RESPONSIBILITIES WHATSOEVER WITH RESPECT TO THE SPECIFICATION OR SUCH PRODUCTS.

4. A NON-EXCLUSIVE COPYRIGHT LICENSE IS HEREBY GRANTED TO REPRODUCE THIS SPECIFICATION FOR ANY PURPOSE PROVIDED THIS “IMPORTANT INFORMATION AND DISCLAIMERS” SECTION (PARAGRAPHS 1-4) IS PROVIDED IN WHOLE. NO OTHER LICENSE, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, TO ANY OTHER INTELLECTUAL PROPERTY RIGHTS IS GRANTED HEREIN.

Intel is a trademark or registered trademark of Intel Corporation or its subsidiaries in the United States and other countries.

Version 1.0a, February 2004

† Other names and brands may be claimed as the property of others.

Copyright 2003, 2004 Intel Corporation. All rights reserved.


Revision History

Version Description Date 1.0 Initial release. September 2003 1.0 a Incorporated Errata A and other editorial changes. February 2004


Contents

1. Introduction...................................................................................................................7 1.1 Terminology ....................................................................................................................................... 8 1.2 Related Documents ........................................................................................................................... 8

2. Form Factor Overview ..................................................................................................9

3. Mechanical Requirements............................................................................................11 3.1 Motherboard Size and Mounting Hole Placement............................................................................. 11 3.2 Volumetric Zones............................................................................................................................... 13

3.2.1 Motherboard Volumetric Zones ............................................................................................ 14 3.2.2 Chassis Volumetric Zones.................................................................................................... 17

3.3 Chassis Mechanical Interfaces.......................................................................................................... 19 3.3.1 Chassis Interface for EMC Grounding.................................................................................. 19 3.3.2 Chassis Interface to Support and Retention Module............................................................ 19 3.3.3 Chassis Interface to Thermal Module................................................................................... 22 3.3.4 Chassis Rear Panel I/O Interface Requirements ................................................................. 24

3.4 Motherboard Mechanical Interfaces .................................................................................................. 25 3.4.1 Motherboard Rear Panel Interface Requirements ............................................................... 25

4. Electrical Interface Requirements ...............................................................................27 4.1 Motherboard Power Supply Connectors ........................................................................................... 27 4.2 Motherboard Power and Control Signal Definitions .......................................................................... 28

4.2.1 +5VSB................................................................................................................................... 28 4.2.2 PS_ON#................................................................................................................................ 28 4.2.3 PWR_OK .............................................................................................................................. 28 4.2.4 Voltage Tolerances............................................................................................................... 29

5. Additional Information..................................................................................................31


Figures Figure 1. Example BTX Board and System Layouts.................................................................................. 9 Figure 2. BTX Form Factor Board and Mounting Hole Dimensions........................................................... 12 Figure 3. Chassis and Motherboard Volumetric Zones (not all zones are shown) .................................... 13 Figure 4. Motherboard Primary Side Volumetric Zone............................................................................... 15 Figure 5. Motherboard Secondary Side Volumetric Zones ........................................................................ 16 Figure 6. Chassis Volumetric Zones .......................................................................................................... 18 Figure 7. Chassis Interface to SRM Requirements.................................................................................... 20 Figure 8. Chassis Interface to SRM Requirement Details ......................................................................... 21 Figure 9. Chassis to Thermal Module Interface and Relation to Chassis and Motherboard Zones .......... 22 Figure 10. Chassis Requirements for Thermal Module Interface Definition .............................................. 23 Figure 11. Chassis Rear Panel I/O Aperture Requirements ...................................................................... 24 Figure 12. Motherboard Rear Panel I/O Aperture Requirements .............................................................. 25 Figure 13. Power Supply Connectors......................................................................................................... 27 Figure 14. Power Timing ............................................................................................................................ 29

Tables Table 1. BTX Feature Summary................................................................................................................. 7 Table 2. Specification Quick Reference ..................................................................................................... 7 Table 3. Terminology.................................................................................................................................. 8 Table 4. Related Documents...................................................................................................................... 8 Table 5. Reference Datums ....................................................................................................................... 11 Table 6. Board Size Options....................................................................................................................... 11 Table 7. Categories and Requirements for Motherboard Volumetric Zones ............................................. 14 Table 8. Categories and Requirements for Chassis Zones ....................................................................... 17 Table 9. Chassis Mechanical Interface Requirements............................................................................... 19 Table 10. Power Supply Connectors.......................................................................................................... 27 Table 11. PS_ON# Signal Characteristics ................................................................................................. 28 Table 12. PWR_OK Signal Characteristics................................................................................................ 29 Table 13. DC Output Voltage Tolerances .................................................................................................. 29


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1. Introduction

The Balanced Technology Extended (BTX) interface specification was developed to provide standard interfaces and form factor definitions to address the electrical, thermal, and mechanical attributes of desktop computer systems. The specification is intended to allow for a wide variety of product differentiation that can be adapted to multiple applications and usage models.

This specification describes the critical mechanical and electrical interfaces for the design of chassis, motherboard, power supply, and other system components necessary for hardware vendors and integrators to build and integrate compliant components, systems, and devices that are interoperable with each other. The intention of this document is not to provide all requirements necessary to design any one of these components, but instead to provide standard interfaces for the components to be designed around.

Table 1 summarizes some of the key features enabled by the BTX specification.

Table 1. BTX Feature Summary

Features Benefits Low profile options Easy integration in small, thin form factor systems In-line core layout Optimized for efficient system cooling Scaleable board dimensions

Multiple system sizes and configurations

Structural board support mechanisms

Mechanical characteristics to support high-mass motherboard components

Table 2 details the interfaces defined in this specification and the section(s) that address each.

Table 2. Specification Quick Reference

Interfaces Features Defining Interface Related Section(s) Motherboard geometry and mounting hole locations (mechanical)

Section 3.1

Motherboard volumetric zones (mechanical) Section 3.2

Chassis volumetric zones (mechanical) Section 3.2.2

Board/Chassis Interfaces

Rear panel chassis I/O locations and openings (mechanical)

Section 3.3.4 and Section 3.4.1

Main power connector (electrical and mechanical)

Section 4 Board/Power Supply Interfaces

+12V power connector (electrical and mechanical)

Section 4

Chassis interface to SRM (mechanical) Section 3.3.2 Chassis interfaces to other components

Chassis interface to Thermal Module (mechanical)

Section 3.3.3


1.1 Terminology Table 3 explains terms introduced in this specification.

Table 3. Terminology

Term Definition Support and Retention Module (SRM)

System component that is assembled to the chassis beneath the motherboard to provide structural support for motherboard and components as well as retention for a thermal module.

Thermal Module A system component with the primary role of dissipating heat from the core components. A typical thermal module includes a heatsink for the processor, an air mover such as an axial fan, and a duct to isolate and direct airflow through the system. The flexibility to adapt to many applications is offered through the option to integrate a range of cooling technologies and components to create a thermal module. Modules will be one of two types based on which Zone A component height maximum (see Figure 4, page 15) is selected: Type I (Standard Height ) or Type II (Low Profile).

1.2 Related Documents Table 4 lists documents related to this specification.

Table 4. Related Documents

Specification Location PCI Express* Specifications http://www.pcisig.com/specifications/pciexpress/ Conventional PCI Specifications http://www.pcisig.com/specifications/conventional/ ATX and microATX Specifications http://www.formfactors.org


2. Form Factor Overview

This specification allows the processor, chipset, memory, add-in cards, and other components to be designed and located in a way that facilitates both efficient motherboard routing and cooling of the components. It also allows options for system layouts that can accommodate a range of profiles and sizes – from compact systems and devices to large, very expandable systems.

The power supply connectors and interfaces are defined to be compatible with those defined for the ATX family of form factors. For more information on standard power supply definitions and the ATX form factor family, see the references listed in Chapter 5.

Figure 1 shows three examples of the many layouts possible with the BTX form factor.

OM16305

Expandable Tower (Side View)

Note: Illustrations not to scale

Desktop (Top View)

Small Form Factor (Top View)

Rear Panel I/O

PowerSupply

Unit

Thermal Module

System/Processor Fan(s)

Cha

ssis

Hard Drive

Mobile OpticalDrive

System Memory

I/O Card Slots

Power Supply Unit

Thermal Module

System/Processor Fan(s)

I/O Card on Riser

Front Side I/OPeripherals

Cha

ssis

System Memory

OpticalDisk Drive

Rear Panel I/O

I/O Card Slots

Rea

r Pan

el I/

OSystem Memory

Processor

Thermal Module

Optical Disk Drive

Optical Disk Drive

Floppy Disk Drive

Hard Disk Drive

Power SupplyUnit

Syst

em/P

roce

ssor

Fan

(s)

Cha

ssis

Front Side I/OPeripherals

Processor

Processor

Figure 1. Example BTX Board and System Layouts


3. Mechanical Requirements

This chapter describes the mechanical requirements of BTX system components and the associated interfaces.

Reference Datums are maintained throughout the drawings in this chapter. Table 5 lists the Datums and the figure in which they are defined.

Table 5. Reference Datums

Datum Defined A Figure 2 B Figure 2 C Figure 2 E Figure 7 G Figure 6 H Figure 6 J Figure 6 P Figure 7

3.1 Motherboard Size and Mounting Hole Placement A BTX board must adhere to the mechanical details depicted in Figure 2. All boards must be 266.70 mm deep. The board width may range from 203.20 mm to 325.12 mm per Table 6. Table 6 lists typical board sizes and the mounting holes required for the motherboard. A BTX chassis must provide mounting points and should provide add-in card apertures in the rear panel for the largest board that it is intended to support.

Table 6. Board Size Options

Board Designation

Maximum Board Width

Maximum Number of Add-in Card Slots Available

Required Mounting Hole Locations

Notes

picoBTX 203.20 mm 1 A, B, C, D microBTX 264.16 mm 4 A, B, C, D, E, F, G BTX 325.12 mm 7 A, B, C, D, E, F, G, H, J, K


OM16309

Notes: 1. Card connector slot centerline. 2. Connector key centerline. 3. Connector pin 1 reference. 4. picoBTX board (maximum 1 slot) 5. microBTX board (maximum 4 slots) 6. BTX board (maximum 7 slots) 7. Tolerance unless otherwise noted ± 0.25 [0.010].

124.00[4.882]

(97.91)[3.855] 2

(35.04)[1.380] 3

Example PCIConnectors

313.

69[1

2.35

0]1

293.

37[1

1.55

0]1

232.

41[9

.150

]1

212.

09[8

.350

]1

273.

05[1

0.75

0]1

252.

73[9

.950

]1

191.

77[7

.550

]1

32

Add-in Card Connector X Direction Location

(39.09) [1.539](60.61) [2.386](60.61) [2.386](35.04) [1.380](35.04) [1.380]

X

50.59 [1.992]103.11 [4.059]83.11 [3.272]49.64 [1.954]97.91 [3.855]

X

PCI ExpressAGP 1.5VAGP 3.3VPCI 3.3VPCI 5V

Card type

Example PCI ExpressConnectors

203.20[8.000] 4

191.

77[7

.550

]

232.

41[9

.150

]

293.

37[1

1.55

0]

264.16[10.400] 5

325.12[12.800] 6

254.00[10.000]

C1.58 +0.20- 0.13

[0.062 ]+0.008- 0.005

A

(39.09)[1.539] 3

(50.59)[1.992] 2

266.70[10.500]

B6.35 ± 0.13

[0.250 ± 0.005]

0.000

Rear Panel I/O

5.08

± 0

.13

[0.2

00 ±

0.0

05]

0.00

0

X

Y

Mounting Holes

Ø 0.20 [0.008] A B C

10X Ø 3.96 +0.05- 0.03

[0.156 ]+0.002- 0.001

A E HC

F

GB D K

J

View Orientation Defined byThird Angle Projection

Figure 2. BTX Form Factor Board and Mounting Hole Dimensions


3.2 Volumetric Zones Volumetric zones are defined to provide a definition for mechanical requirements for each of the key system components areas. These definitions allow components in these areas to be designed separately and integrated without interference.

This section describes volumetric zones based from the motherboard planar (referred to as motherboard zones – Section 3.2.1), volumetric zones based from the chassis (referred to as chassis zones – Section 3.2.2), and the placement requirements for all system components with respect to the zones. These requirements ensure that key system components do not mechanically interfere when they are integrated into a system.

Figure 3 shows some of these zones. Zones A, B, C, and D are motherboard zones and Zones F, G, and H are chassis zones. Not shown in this figure are chassis zones J and K (under the motherboard).

Note that some zones, like Zone A and Zone F, have two heights associated with them. This is to accommodate the two types (heights) of thermal modules and the corresponding system designs. Type I (Standard Height) is intended to be utilized where space is available to maximize the volume available for the thermal module solution design, while Type II (Low Profile) is included as an option for designs where lower profile components in this area are highly valued.

OM16311

Zone B

Zone C

Zone D

Zone A

Zone F

Zone G

Zone H

MotherboardZone H

Type IIType I

Figure 3. Chassis and Motherboard Volumetric Zones (not all zones are shown)


3.2.1 Motherboard Volumetric Zones Sections 3.2.1.1 and 3.2.1.2 define the footprint and height constraints that comprise the overall motherboard volumetric zones. All components in a BTX-compatible system must adhere to the motherboard volumetric zones according to the requirements in Table 7.

Table 7. Categories and Requirements for Motherboard Volumetric Zones

Category Examples Requirements Motherboard components

Memory modules, processors, rear panel motherboard connectors, rigid portions of motherboard-terminated cable assemblies, component heatsinks, components soldered to motherboard

Must fit completely within the motherboard volumetric zones (primary and secondary side)

Chassis components

Chassis walls, chassis pan, motherboard mounting features, peripheral mounting brackets

Must not intersect the motherboard volumetric zone at any point. In addition, adequate clearance should be provided between the chassis, the motherboard volumetric and installed system components to avoid component interference and/or damage during shipping or other dynamic conditions.

Transition components

Add-in cards, air ducts, Thermal Module, SRM, flexible cabling from the motherboard to other system components, motherboard EMC grounding features

May cross the outer boundary of the motherboard volumetric zone. Some of these components, such as add-in cards, may have their own mechanical volumetric specifications which should be considered by the designer in addition to those specified in this document. The Thermal Module can reside across multiple zones (typically Zones A, C, F, G, and H. The Thermal Module should not intersect the top boundaries of any of the volumetric zones.

Other System components

Disk drives, front panel cards, system power supply, and other system components not listed above

Must not intersect the motherboard volumetric zone at any point. In addition, adequate clearance should be provided between installed system components and the motherboard volumetric zone to avoid component interference and/or damage during shipping or other dynamic conditions.


3.2.1.1 Motherboard Primary Side Volumetric Zones Motherboard primary side volumetric zones are defined in Figure 4 . All areas are defined from the top surface of the motherboard.

OM16304

Notes:1. No components or traces allowed in the crosshatched areas.2. To avoid mechanical interference, motherboard and chassis designers who choose to support add-in cards in zone "D" should observe additional mechanical constraints imposed by the add-in card specifications.

A

2

B

0.000

C

162.80[6.409]

0.00

0

50.8

0[2

.000

]

176.

50[6

.949

]

(325.12)[12.800]

(266.70)[10.500]

Zone D34.30 [1.350]

Zone A86.00 [3.386] - Type I60.60 [2.386] - Type II

Zone B34.30 [1.350]

Zone C38.10 [1.500]

62.5

0[2

.461

] 10X Ø 10.92[0.430]


Figure 4. Motherboard Primary Side Volumetric Zone


3.2.1.2 Motherboard Secondary Side Zones Motherboard secondary side volumetric zones are defined in Figure 5. All areas are defined from the bottom surface of the motherboard.

Also defined in Figure 5 are areas for inclusion of optional EMC features. If needed, EMC grounding features extending from the motherboard to the chassis should only be designed within these areas to ensure contact with the corresponding areas reserved in the chassis below the board for this purpose.

All zone boundaries are defined to avoid interference with components in the assembled condition. Additional clearances based on target assembly processes may need to be incorporated.

No components or traces allowed

7.00 [0.276] height

7.00 [0.276] height. Height restriction does not applyto components maintaining conductive path betweenmotherboard and chassis for EMI purposes. Refer tocorresponding chassis requirements in Figure 6.

No components allowed(cone shape volume, Ref section A-A)

4.50 [0.177] height

A

Section A-A

10X Detail A8X Truncated Zones Near Board Edge

A A

(Ø 25.00)[0.984]

10.16[0.400](Ø 10.16)

[0.400]

See Detail A

(325.12)[12.800]

B

0.000

11.70[0.461]

2X 62.65[2.467] 2X 72.53

[2.856]

2X 102.53[4.037]

2X 82.65[3.254]

110.00[4.331]122.00

[4.803]

2X 97.00[3.819]

2X 157.00[6.181]

(254.00)[10.000]

C10X Ø 10.16[0.400]

10X (Ø 3.96)[0.156]

5.50[0.217]

(266.70)[10.500]

(124.00)[4.882]

0.00

0

34.3

2[1

.351

]

13.0

0[0

.512

]

41.3

2[1

.627

]35

.00

[1.3

78]

149.

17[5

.873

]

50.1

7[1

.975

]

78.1

7[3

.078

]

118.

67[4

.672

]10

8.67

[4.2

78]

177.

17[6

.975

]15

7.00

[6.1

81]

186.

02[7

.324

]

191.

20[7

.528

]

(191

.77)

[7.5

50]

197.

50[7

.776

]19

3.02

[7.5

99]

(232

.41)

[9.1

50]

(293

.37)

[11.

550]

OM16301

0.64[0.025]

0.64[0.025]

10X Ø 25.00[0.984]

A


Note: Main view as viewed from motherboard secondary side.

Figure 5. Motherboard Secondary Side Volumetric Zones


3.2.2 Chassis Volumetric Zones Figure 6 defines the footprint and heights that comprise the chassis volumetric zones as referenced from the top surface of the chassis pan. All components in a BTX-compatible system must adhere to the chassis volumetric zones according to the requirements in Table 8. Note that although Figure 6 shows the zones for the widest motherboard (seven slot board), rules for Zone J scale according to the width of the motherboard being used. Requirements in this section do not affect the volume beyond the extensible edge of the motherboard that the system is designed to accommodate.

Table 8. Categories and Requirements for Chassis Zones

Category Examples Requirements Motherboard Components

Memory modules, processors, rear panel motherboard connectors and rigid portions of motherboard-terminated cable assemblies, component heatsinks, and components soldered to motherboard

Must not intersect any of the chassis volumetric zones at any point. In addition, adequate clearance should be provided between installed system components and the chassis volumetric to avoid component interference and/or damage during shipping or other dynamic conditions.

Chassis Components

Chassis pan, board mounting features, and drive bays

Must not intersect volumetric zones F, G, or H. Chassis features in Zone K must not cross the upper boundary of Zone K. Only the interface features called out in Figure 7 and Figure 8 are allowed in Zones F, G, H, and J. No other chassis features should intersect this zone. Board mounting features should stay within the zones specified for these features.

Transition Components

SRM and Thermal Module May cross the outer boundary of some chassis zones. Components such as an SRM may have their own requirements which should be considered by the designer in addition to those specified in this document.

Other System Components

Disk drives and system power supply

Must not intersect any of the chassis volumetric zones at any point. In addition, adequate clearance should be provided between installed system components and the chassis volumetric to avoid component interference and/or damage during shipping or other dynamic conditions.


97.75 [3.848] height off datum : Type I thermal moduleJ72.35 [2.848] height off datum : Type II thermal moduleJ

50.09 [1.972] height off datum J

0.000

305.35[12.022]

2X 302.85[11.923]

50.8

0[2

.000

]

41.0

3[1

.615

]

62.5

0[2

.461

]

176.

50[6

.949

]18

6.27

[7.3

33]Interface Plane

Zone F

Zone G

11.75 [0.463] height off datum Volume shared with chassis pan guide featuresas specified in Figure 7 (Ref Detail A).

J

3.16 [0.124] height off datum J

Zone H

3.16 [0.124] height off datum No feature placement with exception of thosefeatures defined in Figure 7.

J

Zone K

Zone J

Denotes cone shape chassis keep-in volume as depicted in Detail A.Motherboard mounting feature must stay within this volume.

OM16302

Zone

G

Zone F

Zone J

Zone K

J

Section A-A

10X Detail A8X Truncated Volumes

A A

(Ø 10.16)[0.400]

10.16[0.400]

(Ø 25.00)[0.984]

0.00

0

5.08

[0.2

00]

(191

.77)

[7.5

50]

(29.

21)

[1.1

50]

(232

.41)

[9.1

50]

(293

.37)

[11.

550]

320.

04[1

2.60

0]

6.35[0.250]

(124.00)[4.882]

260.35[10.250]

198.

12[7

.800

]

G

H

(260.35)[10.250]

(5.50)[0.217]

10X Ø 25.00[0.984]

10X Ø 10.16[0.400]

Zone KZo

ne H

Zone

H

See Detail A

J

Chassis PanPlanar


Figure 6. Chassis Volumetric Zones


3.3 Chassis Mechanical Interfaces In addition to the other mechanical requirements in this specification, a BTX chassis should provide the interface features listed in Table 9.

Table 9. Chassis Mechanical Interface Requirements

Mechanical Interface Features Reference Areas on the chassis pan for interface with board EMC grounding features

Figure 7

Attach features for a Support and Retention Module (SRM) Figure 7 and Figure 8. Common interface to a thermal module Section 3.3.3, Figure 10 Rear panel aperture for interface with the motherboard rear panel connectors

Section 3.3.4, Figure 11

3.3.1 Chassis Interface for EMC Grounding The chassis should allow areas as shown in Figure 7 to interface with the grounding features on the motherboard. These areas must be unpainted and allow conduction to chassis for grounding.

3.3.2 Chassis Interface to Support and Retention Module A Support and Retention Module, or SRM, is a system component that can be used to support an area of the motherboard and loads upon the motherboard such as loads associated with a Thermal Module. An SRM can reside in chassis volumetric zone J and also may share chassis zone K as well as the secondary side motherboard zone. A BTX chassis must include interfaces as defined by the features shown in Figure 7 to provide a standard interface for SRMs. Accordingly, an SRM for a BTX chassis and motherboard should be designed to fit into and mate with these features. The interface between the SRM and the motherboard will vary depending on the motherboard and thermal module design.


OM16310

4.45

[0.1

75]

0.00

0

157.

00[6

.181

]

191.

20[7

.528

](1

91.7

7)[7

.550

]19

7.50

[7.7

76]

(232

.41)

[9.1

50]

13.0

0[0

.512

]35

.00

[1.3

78]

J E

10.16 ± 0.10[0.400 ± 0.004]

Chassis RearPanel

0.000

See Detail B,Figure 8

185.00[7.283]

200.00 ± 0.50[7.874 ± 0.020]

160.10 ± 0.30[6.303 ± 0.012]

153.00 ± 0.30[6.024 ± 0.012]

Notes:1. Chassis datum axes and are coincident to motherboard datum axes and and simulated by chassis to motherboard fastening features. Chassis datum axis corresponds to motherboard elevation plane as simulated by chassis fastening features.

G HB C

E

2. 6-32 threaded standoff with height of 3.00 ± 0.15 [0.118 ± 0.006] above datum and Ø 7.11 ± 0.12 [0.280 ± 0.005] required.3. All critical interface features are dimensioned. All other features shown for reference only.

G

H

5.72[0.225]

11.70[0.461]

2X 97.00[3.819]

2X 157.00[6.181]

(254.00)[10.000]

(124.00)[4.882]See Detail C,

Figure 8

See Detail A,Figure 8

99.00[3.898]

272.53[10.730]

2X 7.91 ± 0.30[0.311 ± 0.012]

10.00 ± 0.50[0.394 ± 0.020]

55.88[2.200]

111.76[4.400]

2X 16.97[0.668]

57.7

9[2

.275

]

P

Ø 0.25 [0.010] J P

2X 145.70 ± 0.25 [5.736 ± 0.010]

Ø 0.25 [0.010] J G H

2X 2

6.38[0.251]

J

Flat EMI contact area at elevation of datum to be free of paint and coatingsthat would prevent electrical contact with motherboard enabled feature[s].

J


MotherboardElevation

4. Implement only on two front guide features. Omit on two rear guide features.

Figure 7. Chassis Interface to SRM Requirements


J

Section C-C

(2.32)[0.091]

3.80 Max[0.150]

20.00 Max[0.787]

J

(5.63)[0.222]

Section B-B

4X R0.75 Max [0.030]

(13.00)[0.512]

2X 3.69 ± 0.30 [0.145 ± 0.012]

2X 2.32 ± 0.20 [0.091 ± 0.008]

2X 2.00 ± 0.25 [0.079 ± 0.010]

J

4X Detail AGuide

(7.91)[0.311]

2X R1.0 Max [0.039]

4

2.20 ± 0.20[0.087 ± 0.008]

4

A

A

6.00 Max[0.236]

Section A-A

16.00 Max[0.630]

J

2.50 ± 0.25[0.098 ± 0.010]

4

3.50 ± 1.00[0.138 ± 0.039]

OM16313

Section D-D

3.00 ± 0.25[0.118 ± 0.010]

J

R0.50 Max [0.020]

26.00 Max[1.024]

BB

C

C

2X Detail BRetainer Slot

26.00 Max[1.024]

0.40 [0.016] J P

5.63 ± 0.20 [0.222 ± 0.008]

0.50 [0.020] J P

3.00 ± 0.50 [0.118 ± 0.020]

Detail CRetainer Tab

7.10 ± 0.30[0.280 ± 0.012]

(55.88)[2.200]

DD

1.00 [0.039] M J P

7.10 [0.280] Max

Notes:1. Chassis datum axes and are coincident to motherboard datum axes and and simulated by chassis to motherboard fastening features. Chassis datum axis corresponds to motherboard elevation plane as simulated by chassis fastening features.

G HB C

E

2. 6-32 threaded standoff with height of 3.00 ± 0.15 [0.118 ± 0.006] above datum and Ø 7.11 ± 0.12 [0.280 ± 0.005] required.3. All critical interface features are dimensioned. All other features shown for reference only.4. Implement only on two front guide features. Omit on two rear guide features.

J


Figure 8. Chassis Interface to SRM Requirement Details


3.3.3 Chassis Interface to Thermal Module In order to provide a standard interface between a thermal module and the chassis, a common physical interface plane and geometry are required. Figure 9 shows the relationship between the motherboard zones (Section 3.2.1), the thermal module, the chassis/thermal module interface, and the chassis zones (Section 3.2.2).

OM16312

Zone B

Zone C

Zone D

Zone A

Zone F

Zone G

Zone H

Zone H

Thermal Module

To ChassisInlet Vent

ChassisDuct Interface

Figure 9. Chassis to Thermal Module Interface and Relation to Chassis and Motherboard Zones


Figure 10 defines both a plane relative to the motherboard datums as well as the surface geometry that should be provided on that plane by the chassis (and designed for the thermal module). The surface consists of a frame of minimum width around the window defined for airflow to the thermal module.

The primary purpose for this interface and connection is to provide external air from a vent in the chassis to the thermal module. For this reason, the air channel and the chassis vent should be designed so that there is minimal impedance to airflow from outside the chassis to the defined interface.

OM16303

Notes:1. Chassis datum axis and are coincident to motherboard datum axis and as simulated by chassis to motherboard fastening features. Chassis datum plane corresponds to bottom side of motherboard as simulated by chassis to motherboard fastening features. Chassis datum plane corresponds to the top surface of the chassis bottom.

G HB C

E

J

2. Airflow volume between interface plane and chassis airflow inlet shall be isolated from internal chassis volume to prevent re-circulation of air.3. Do not place any topographical features in this area on the thermal module interface plane side.4. All dimensions basic unless indicated otherwise.5. Applicable to Type I system.6. Applicable to Type II system.

305.

35 ±

0.5

0[1

2.02

2 ±

0.02

0]

System Front

J

E

JChassis Bottom

Motherboard Elevation

(98.00)[3.858]

92.00[3.622]

0.00

0

2X 3.00[0.118]

Interface area tothermal module 3

E

5

67.67[2.664]

6.00[0.236]

87.25[3.435]

661.85[2.435]

5(97.25)[3.829]

6(71.85)[2.829]Airflow Inlet Area

2X 4.00[0.157]

(2.00)[0.079]

Interface Plane 2


GH G

Figure 10. Chassis Requirements for Thermal Module Interface Definition


3.3.4 Chassis Rear Panel I/O Interface Requirements Figure 11 defines the chassis cutout window and associated margins for interface with the rear panel I/O shield.

OM16307

Notes: 1. Do not place any topographical features in this area on either the inside or the outside surface of chassis rear panel. Do not paint this area. 2. Datum axis is coincident to datum of motherboard. 3. Chassis datum plane corresponds to bottom side of motherboard as simulated by chassis fastening features. Chassis datum plane corresponds to the top surface of the chassis bottom.

E

8.46 ± 0.25[0.333 ± 0.010]

1.32 [0.052]0.79 [0.031]Allowable wall thickness

169.54 ± 0.20[6.675 ± 0.008]

2.16 ± 0.25[0.085 ± 0.010]

39.45 ± 0.20[1.553 ± 0.008]

1

2.47 ± 0.25[0.097 ± 0.010]

4X R1.0 [0.039] MaxTyp

Motherboardmount feature

Chassis I/O aperture should be a simple cutout of thechassis rear panel. Recessing the I/O aperture will

prevent the case from accepting compliant I/O shields.

2.29 [0.090] Min keepoutaround opening

J

Chassis I/O Aperture E

G

G

J

(10.16)[0.400]

G BE

J


Figure 11. Chassis Rear Panel I/O Aperture Requirements


3.4 Motherboard Mechanical Interfaces

3.4.1 Motherboard Rear Panel Interface Requirements All rear panel external motherboard connectors (and their mating cable connectors) must pass through the motherboard rear panel I/O shield within the shaded window depicted in Figure 12.

OM16306

Notes: 1. Bottom of motherboard is coincident with datum . 2. Datum is coincident with datum .

A A

B 2

B 2

7.49 ± 0.20[0.295 ± 0.008]

(6.35)[0.250]

I/O ConnectorProtrusion Area

168.78 Max[6.645]Motherboard

1

E

GB

5.08 Min[0.200]

Connector's Protruding Feature

Connector Face

32.47 [1.278] Max


Figure 12. Motherboard Rear Panel I/O Aperture Requirements


4. Electrical Interface Requirements

4.1 Motherboard Power Supply Connectors Figure 13 defines the required pinout for the required connectors listed in Table 10. The connectors provide a standard interface between a BTX motherboard and a compatible system power supply. Further information on critical signals is defined in Section 4.2. For additional information on the design of compatible system power supplies, refer to the design guides at the location listed in Section 5.

Table 10. Power Supply Connectors

Connector Description

Status Board-mounted Header

Mating Power Supply Receptacle

Electrical Signal Implementation

Main Power Connector Required on all motherboards

Molex† 44206-0007 or equivalent

Molex† 39-01-2240 or equivalent

Per Figure 13 and Section 4.2

+12V Power Connector Required on all motherboards



Per Figure 13 and Section 4.2

OM16308

+3/3VDC

-12VDC

COM

PS_ON#

COM

COM

COM

NC

+5VDC

+5VDC

+3.3VDC

Pin 13 Pin 1

+3.3VDC

COM

+5VDC

COM

+5VDC

COM

PWR_OK

+5VSB

+12VDC

+5VDC

COM

+12VDC

+3.3VDC

+12VDC

+12VDC

COM

Pin 3 Pin 1

COM

+12V Power Connector

Main Power Connector

Figure 13. Power Supply Connectors


4.2 Motherboard Power and Control Signal Definitions

4.2.1 +5VSB +5VSB is a standby voltage supply that is active whenever AC power is present to the system power supply. It provides a power source for circuits that must remain operational when the three main DC outputs (+12VDC, +5VDC, +3.3VDC) are in a disabled state. Example uses include soft power control, Wake on LAN technology, wake-on-modem, intrusion detection, or suspend (sleep) state activities. The maximum current available from the +5VSB output depends on the design of the system power supply.

4.2.2 PS_ON# PS_ON# is an active low, TTL-compatible signal that allows the motherboard to enable the three main system power supply DC output rails (+3.3VDC, +5VDC, +12VDC). PS_ON# is pulled up to +5VSB via a 10 kΩ resistor internal to the system power supply.

When PS_ON# is pulled to TTL low, the DC outputs are enabled by the system power supply.

When PS_ON# is held to TTL high by the motherboard or left open circuited, the system power supply shall not deliver current at the main DC outputs and shall hold them at zero potential with respect to ground.

Table 11. PS_ON# Signal Characteristics

Min. Max. VIL, Input Low Voltage 0.1 V 0.8 V IIL, Input Low Current, Vin = 0.4 V -1.6 mA VIH, Input High Voltage, Iin = -200 µA 2.0 V VIH open circuit, Iin = 0 5.25 V

4.2.3 PWR_OK PWR_OK is a power good signal asserted by the system power supply to indicate that the +5VDC, +3.3VDC, and +12VDC outputs are above the undervoltage thresholds of the power supply. When this signal is asserted high, the system power supply has sufficient energy stored by the converter to guarantee continuous power operation for a minimum hold-up time per the system power supply’s specification. Conversely, when one or more of the output voltages fall below their undervoltage threshold, or when mains power has been removed for a time sufficiently long so that power supply operation is no longer guaranteed beyond the hold up time, PWR_OK will be de-asserted to a low state by the power supply.


Table 12. PWR_OK Signal Characteristics

Parameter Value Signal type +5 V TTL compatible Logic level low < 0.4 V while sinking 4 mA Logic level high Between 2.4 V and 5 V output while sourcing 200 µA High-state output impedance 1 kΩ from output to common PWR_OK delay 100 ms < T3 < 500 ms PWR_OK rise time T4 ≤ 10 ms AC loss to PWR_OK hold-up time T5 ≥ 16 ms Power-down warning T6 ≥ 1 ms

OM16314

VAC

PS_ON#

PWR_OK

O/P's+12VDC+5VDC

+3.3VDC

T1

T4

T5

95%

10%

T3

T2

T6

Figure 14. Power Timing

4.2.4 Voltage Tolerances The system power supply shall guarantee that the tolerances for the main DC outputs comply with the values listed in Table 13, subject to the limits of the system power supply’s specified capabilities.

Table 13. DC Output Voltage Tolerances

Voltage Rail Tolerance +3.3VDC ± 5% +5VDC ± 5% +12VDC ± 5% -12VDC ± 10% +5VSB ± 5%


5. Additional Information

For additional information beyond the requirements of this specification, refer to:

http:\\www.formfactors.org

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