Balanced Technology Extended (BTX) Interface Specification

Version 1.0b

Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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 1.0b, July 2005

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

Copyright © 2003-2005 Intel Corporation. All rights reserved.

Page 2 Balanced Technology Extended (BTX) Interface Specification Version 1.0b Revision History

Version Description Date 1.0 Initial release. September 2003 1.0a Incorporated Errata A and other editorial changes. February 2004 1.0b Added nanoBTX form factor. July 2005

Page 3 Balanced Technology Extended (BTX) Interface Specification Version 1.0b 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

Page 4 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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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Page 6 Balanced Technology Extended (BTX) Interface Specification Version 1.0b 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 Multiple system sizes and configurations dimensions Structural board support Mechanical characteristics to support high-mass motherboard components mechanisms

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) Board/Chassis Interfaces Motherboard geometry and mounting hole Section 3.1 locations (mechanical) Motherboard volumetric zones (mechanical) Section 3.2

Chassis volumetric zones (mechanical) Section 3.2.2 Rear panel chassis I/O locations and Section 3.3.4 and Section 3.4.1 openings (mechanical) Board/Power Supply Main power connector (electrical and Section 4 Interfaces mechanical) +12V power connector (electrical and Section 4 mechanical) Chassis interfaces to Chassis interface to SRM (mechanical) Section 3.3.2 other components Chassis interface to Thermal Module Section 3.3.3 (mechanical)

Page 7 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

1.1 Terminology

Table 3 explains terms introduced in this specification. Table 3. Terminology

Term Definition Support and Retention Module System component that is assembled to the chassis beneath the (SRM) 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

Page 8 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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.

Expandable Tower (Side View) Desktop (Top View)

Rear Panel I/O Optical Disk Drive I/O Card Slots Power Supply Unit Power Supply Unit Optical Disk Drive

I/O Card on Riser Floppy Disk Drive System Memory

Hard Disk Drive System Memory Chassis Optical

Rear Panel I/O Rear Panel Disk Drive Processor Processor Chassis Thermal Module Thermal Module

System/Processor Fan(s) Front Side I/O System/Processor Fan(s) Peripherals I/O Card Slots

Front Side I/O Small Form Factor (Top View) Peripherals Rear Panel I/O

Power Hard Drive Supply Unit

System Memory

Processor Chassis

Thermal Module Mobile Optical System/ Drive Processor Fan(s)

Note: Illustrations not to scale OM16305

Figure 1. Example BTX Board and System Layouts

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Page 10 Balanced Technology Extended (BTX) Interface Specification Version 1.0b 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 Maximum Maximum Required Mounting Notes Designation Board Number of Add- Hole Locations Width in Card Slots Available picoBTX 203.20 mm 1 A, B, C, D nanoBTX 223.52 mm 2 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

Page 11 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

1 1 1 1 1 1 1

A B Rear Panel I/O 0.000 6.35 ± 0.13 5.08 ± 0.13 [0.200 ± 0.005] 191.77 [7.550] 212.09 [8.350] 273.05 [10.750] 313.69 [12.350] [0.250 ± 0.005] 232.41 [9.150] 252.73 [9.950] 293.37 [11.550] 0.000 A Y C E H X (35.04) (39.09) 3 [1.539] 3 [1.380] (50.59) [1.992] 2

(97.91) [3.855] 2 266.70 [10.500] 124.00 F J [4.882]

Example PCI Express Example PCI Connectors Connectors

+0.05 10X Ø 3.96 - 0.03 +0.002 [0.156 - 0.001 ] 254.00 B D G K [10.000] Ø 0.20 [0.008] A B C Mounting Holes

+0.20 191.77 [7.550] 1.58 C 203.20 232.41 [9.150]

- 0.13 293.37 4 [11.550] +0.008 [8.000] [0.062 - 0.005 ] 223.52 [8.800] 5 264.16 [10.400] 6 325.12 [12.800] 7 Notes: Add-in Card Connector X Direction Location 1 Card connector slot centerline 2 Connector key centerline Card type X 2 X 3 3 Connector pin 1 reference PCI 5V 97.91 [3.855] (35.04) [1.380] 4 picoBTX board (maximum 1 slot) PCI 3.3V 49.64 [1.954] (35.04) [1.380] 5 nanoBTX board (maximum 2 slots) AGP 3.3V 83.11 [3.272] (60.61) [2.386] 6 microBTX board (maximum 4 slots) AGP 1.5V 103.11 [4.059] (60.61) [2.386] 7 BTX board (maximum 7 slots) PCI Express 50.59 [1.992] (39.09) [1.539] 8 Tolerance unless otherwise noted ± 0.25 [0.010]

View Orientation Defined by Third Angle Projection

OM16309A

Figure 2. BTX Form Factor Board and Mounting Hole Dimensions

Page 12 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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.

Zone D

Zone B Zone A

Zone F

Zone C

Motherboard Zone H Type I Zone H Type II Zone G OM16311

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

Page 13 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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 Memory modules, processors, Must fit completely within the motherboard components rear panel motherboard volumetric zones (primary and secondary side) connectors, rigid portions of motherboard-terminated cable assemblies, component heatsinks, components soldered to motherboard Chassis Chassis walls, chassis pan, Must not intersect the motherboard volumetric zone components motherboard mounting at any point. In addition, adequate clearance features, peripheral mounting should be provided between the chassis, the brackets motherboard volumetric and installed system components to avoid component interference and/or damage during shipping or other dynamic conditions. Transition Add-in cards, air ducts, May cross the outer boundary of the motherboard components Thermal Module, SRM, flexible volumetric zone. Some of these components, such cabling from the motherboard as add-in cards, may have their own mechanical to other system components, volumetric specifications which should be motherboard EMC grounding considered by the designer in addition to those features 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 Disk drives, front panel cards, Must not intersect the motherboard volumetric zone components system power supply, and at any point. In addition, adequate clearance other system components not should be provided between installed system listed above components and the motherboard volumetric zone to avoid component interference and/or damage during shipping or other dynamic conditions.

Page 14 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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.

(325.12) [12.800]

A 0.000 50.80 [2.000] 176.50 [6.949] B 0.000

Zone C Zone B 38.10 [1.500] 34.30 [1.350]

(266.70) [10.500]

162.80 [6.409] Zone D 2 34.30 [1.350]

Zone A 86.00 [3.386] - Type I 60.60 [2.386] - Type II

C 10X Ø 10.92 [0.430] 62.50 [2.461] 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.

View Orientation Defined by Third Angle Projection

OM16304

Figure 4. Motherboard Primary Side Volumetric Zone

Page 15 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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.

(325.12) [12.800] (232.41) [9.150] 193.02 [7.599] 191.20 [7.528] 177.17 [6.975] 149.17 [5.873] 108.67 [4.278] 50.17 [1.975] 35.00 [1.378] 13.00 [0.512] 0.64 [0.025] See Detail A A 197.50 [7.776] (191.77) [7.550] 41.32 [1.627] (293.37) [11.550] 186.02 [7.324] 157.00 [6.181] 118.67 [4.672] 78.17 [3.078] 34.32 [1.351] 0.000 B 0.000

11.70 [0.461]

(266.70) 2X 62.65 [10.500] [2.467] 2X 72.53 2X 82.65 [2.856] [3.254] 2X 97.00 2X 102.53 [3.819] [4.037] 110.00 (124.00) [4.331] [4.882] 122.00 [4.803] 10X Ø 25.00 [0.984] 2X 157.00 [6.181]

0.64 [0.025]

(254.00) [10.000] 5.50 10X Ø 10.16 C [0.217] [0.400] 10X (Ø 3.96) [0.156] No components or traces allowed 10.16 (Ø 10.16) [0.400] 4.50 [0.177] height [0.400]

No components allowed A (cone shape volume, Ref section A-A) (Ø 25.00) 7.00 [0.276] height [0.984] Section A-A 7.00 [0.276] height. Height restriction does not apply to components maintaining conductive path between motherboard and chassis for EMI purposes. Refer to corresponding chassis requirements in Figure 6. AA View Orientation Defined by Third Angle Projection 10X Detail A 8X Truncated Zones Near Board Edge Note: Main view as viewed from motherboard secondary side. OM16301

Figure 5. Motherboard Secondary Side Volumetric Zones

Page 16 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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 the portion of Zone K under Zone D 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 Memory modules, processors, Must not intersect any of the chassis volumetric Components rear panel motherboard zones at any point. In addition, adequate clearance connectors and rigid portions should be provided between installed system of motherboard-terminated components and the chassis volumetric to avoid cable assemblies, component component interference and/or damage during heatsinks, and components shipping or other dynamic conditions. soldered to motherboard Chassis Chassis pan, board mounting Must not intersect volumetric zones F, G, or H. Components features, and drive bays 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 SRM and Thermal Module May cross the outer boundary of some chassis Components 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 Disk drives and system power Must not intersect any of the chassis volumetric Components supply 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.

Page 17 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

5.08 [0.200] 0.000 (29.21) [1.150] (191.77) [7.550] 198.12 [7.800] (232.41) [9.150] (293.37) [11.550] 320.04 [12.600] 6.35 0.000 [0.250]

G

Zone K (124.00) Zone K Zone J [4.882] Chassis Pan See Detail A Planar

H

(260.35) 260.35 [10.250] [10.250] Zone F 10X Ø 25.00

Zone H Zone H [0.984] 2X 302.85 Zone G [11.923] 10X Ø 10.16 [0.400] 305.35 (5.50) J [12.022] Interface Plane [0.217] (Ø 25.00) 41.03 50.80 62.50 [1.615] [2.000] [2.461] 176.50 [6.949] 186.27 [7.333] [0.984] 10.16 [0.400] 97.75 [3.848] height off datum J : Type I thermal module J Zone F 72.35 [2.848] height off datum J : Type II thermal module

Zone G 50.09 [1.972] height off datum J

11.75 [0.463] height off datum J (Ø 10.16) Zone H Volume shared with chassis pan guide features [0.400] as specified in Figure 7 (Ref Detail A). Section A-A 3.16 [0.124] height off datum J Zone J No feature placement with exception of those features defined in Figure 7.

Zone K 3.16 [0.124] height off datum J AA Denotes cone shape chassis keep-in volume as depicted in Detail A. Motherboard mounting feature must stay within this volume. 10X Detail A 8X Truncated Volumes View Orientation Defined by Third Angle Projection

OM16302

Figure 6. Chassis Volumetric Zones

Page 18 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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 Figure 7 features 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 Section 3.3.4, Figure 11 connectors

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.

Page 19 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

6.38 99.00 [0.251] 191.20 [7.528] 197.50 [7.776] 4.45 [0.175] 13.00 [0.512] [3.898] Chassis Rear Panel G 0.000 35.00 [1.378] 157.00 [6.181] (191.77) [7.550] (232.41) [9.150] 5.72 0.000 [0.225]

11.70 Motherboard [0.461] Elevation See Detail B, Figure 8

2X 97.00 [3.819]

(124.00) [4.882] 200.00 ± 0.50 See Detail C, [7.874 ± 0.020] Figure 8 2X 157.00 [6.181] 160.10 ± 0.30 [6.303 ± 0.012] 185.00 [7.283] 153.00 ± 0.30 [6.024 ± 0.012]

(254.00) [10.000] 272.53 [10.730] H

10.16 ± 0.10 10.00 ± 0.50 55.88 [0.400 ± 0.004] See Detail A, [0.394 ± 0.020] [2.200] 2X 7.91 ± 0.30 [0.311 ± 0.012] Figure 8 2X 16.97 J E [0.668] 2X 2 111.76 Ø 0.25 [0.010] J G H [4.400] 57.79 P [2.275] 2X 145.70 ± 0.25 [5.736 ± 0.010] Ø 0.25 [0.010] J P

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

Notes: 1. Chassis datum axes G and H are coincident to 2. 6-32 threaded standoff with height of 3.00 ± 0.15 motherboard datum axes B and C and simulated [0.118 ± 0.006] above datum J and Ø 7.11 ± 0.12 by chassis to motherboard fastening features. [0.280 ± 0.005] required. Chassis datum axis E corresponds to motherboard 3. All critical interface features are dimensioned. elevation plane as simulated by chassis fastening All other features shown for reference only. features. 4. Implement only on two front guide features. Omit on two rear guide features. View Orientation Defined by Third Angle Projection

OM16310

Figure 7. Chassis Interface to SRM Requirements

Page 20 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

C 5.63 ± 0.20 [0.222 ± 0.008] 0.40 [0.016] J P 3.50 ± 1.00 (2.32) [0.138 ± 0.039] 6.00 Max [0.091] [0.236] 2.50 ± 0.25 4 [0.098 ± 0.010] A 3.00 ± 0.50 [0.118 ± 0.020] (7.91) 0.50 [0.020] J P [0.311] B B 20.00 Max [0.787] 16.00 Max [0.630] 26.00 Max [1.024] 2X R1.0 Max 4 [0.039]

2.20 ± 0.20 4 [0.087 ± 0.008] J A 3.80 Max Section A-A 4X Detail A [0.150] Guide J C 26.00 Max 3.00 ± 0.25 Section C-C [1.024] [0.118 ± 0.010] J 2X Detail B Retainer Slot Notes: R0.50 Max 1. Chassis datum axes G and H are coincident to [0.020] motherboard datum axes B and C and simulated (5.63) [0.222] Section D-D by chassis to motherboard fastening features. J Chassis datum axis E corresponds to motherboard 2X 2.32 ± 0.20 4X R0.75 Max elevation plane as simulated by chassis fastening [0.091 ± 0.008] [0.030] features. 2. 6-32 threaded standoff with height of 3.00 ± 0.15 [0.118 ± 0.006] above datum J and Ø 7.11 ± 0.12 J [0.280 ± 0.005] required. 2X 3.69 ± 0.30 3. All critical interface features are dimensioned. [0.145 ± 0.012] D D All other features shown for reference only. (13.00) [0.512] 7.10 ± 0.30 4. Implement only on two front guide features. 7.10 [0.280] Max [0.280 ± 0.012] Omit on two rear guide features. Section B-B 1.00 [0.039] M J P 2X 2.00 ± 0.25 View Orientation Defined by [0.079 ± 0.010] Third Angle Projection (55.88) [2.200] Detail C Retainer Tab OM16313

Figure 8. Chassis Interface to SRM Requirement Details

Page 21 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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).

Thermal Module

Zone B Zone D Zone A

Zone C Zone F

Zone H

Chassis Duct Interface To Chassis Inlet Vent Zone H Zone G OM16312

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

Page 22 Balanced Technology Extended (BTX) Interface Specification Version 1.0b

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.

(98.00) [3.858] 2X 3.00 92.00 67.67

305.35 ± 0.50 [12.022 ± 0.020] [0.118] [3.622] [2.664] Interface area to System Front thermal module 3 (97.25) [3.829] 5 (71.85) Interface Plane Airflow Inlet Area 2 [2.829] 6 87.25

0.000 [3.435] 5 Motherboard Elevation E (2.00) 61.85 E [0.079] [2.435] 6

H Chassis Bottom G J J 2X 4.00 6.00 G [0.157] [0.236]

Notes: 2. Airflow volume between interface plane and chassis airflow inlet shall be isolated from 1. Chassis datum axis G and H are coincident to motherboard datum axis internal chassis volume to prevent re-circulation of air. B and C as simulated by chassis to motherboard fastening features. 3. Do not place any topographical features in this area on the thermal module interface plane side. Chassis datum plane E corresponds to bottom side of motherboard 4. All dimensions basic unless indicated otherwise. as simulated by chassis to motherboard fastening features. Chassis 5. Applicable to Type I system. datum plane J corresponds to the top surface of the chassis bottom. 6. Applicable to Type II system.

View Orientation Defined by Third Angle Projection

OM16303

Figure 10. Chassis Requirements for Thermal Module Interface Definition

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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.

Chassis I/O aperture should be a simple cutout of the chassis rear panel. Recessing the I/O aperture will prevent the case from accepting compliant I/O shields. 8.46 ± 0.25 [0.333 ± 0.010] 2.29 [0.090] Min keepout 4X R1.0 [0.039] Max 1.32 [0.052] around opening 1 Typ 0.79 [0.031] Allowable wall thickness

(10.16) 39.45 ± 0.20 Chassis I/O Aperture [0.400] E [1.553 ± 0.008] E J

169.54 ± 0.20 2.47 ± 0.25 J [6.675 ± 0.008] [0.097 ± 0.010] Motherboard 2.16 ± 0.25 G mount feature [0.085 ± 0.010] G

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 G is coincident to datum B of motherboard. 3. Chassis datum plane E corresponds to bottom side of motherboard as simulated by chassis fastening features. Chassis datum plane J corresponds to the top surface of the chassis bottom.

View Orientation Defined by Third Angle Projection

OM16307

Figure 11. Chassis Rear Panel I/O Aperture Requirements

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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.

Connector Face B 2 Connector's Protruding Feature 7.49 ± 0.20 [0.295 ± 0.008]

B 2 A 32.47 [1.278] Max I/O Connector A Protrusion Area

5.08 Min (6.35) 1 [0.200] [0.250] 168.78 Max Motherboard [6.645]

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

View Orientation Defined by Third Angle Projection

OM16306

Figure 12. Motherboard Rear Panel I/O Aperture Requirements

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Page 26 Balanced Technology Extended (BTX) Interface Specification Version 1.0b 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 Status Board-mounted Mating Power Electrical Signal Description Header Supply Implementation Receptacle Main Power Connector Required on all Molex† 44206-0007 Molex† 39-01-2240 or Per Figure 13 and motherboards or equivalent equivalent Section 4.2 +12V Power Connector Required on all Molex† 39-29-9042 Molex† 39-01-2040 or Per Figure 13 and motherboards or equivalent equivalent Section 4.2

Pin 13 Pin 1

+3/3VDC +3.3VDC -12VDC +3.3VDC COM COM PS_ON# +5VDC Pin 3 Pin 1 COM COM +12VDC COM COM +5VDC +12VDC COM COM COM +12V Power Connector NC PWR_OK +5VDC +5VSB +5VDC +12VDC +5VDC +12VDC COM +3.3VDC

Main Power Connector OM16308

Figure 13. Power Supply Connectors

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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.

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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

T1 T5

VAC

PS_ON#

+12VDC 95% +5VDC O/P's +3.3VDC 10% T2 T3 PWR_OK

T4 T6 OM16314

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%

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Page 30 Balanced Technology Extended (BTX) Interface Specification Version 1.0b 5. Additional Information

For additional information beyond the requirements of this specification, refer to: http:\\www.formfactors.org

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