Asus M4A785-M - Motherboard - Micro ATX User manual

Motherboard
M4A785-M

ii
Copyright © 2009 ASUSTeK Computer Inc. All Rights Reserved.
No part of this manual, including the products and software described in it, may be reproduced,
transmitted, transcribed, stored in a retrieval system, or translated into any language in any form or by any
means, except documentation kept by the purchaser for backup purposes, without the express written
permission of ASUSTeK Computer Inc. (“ASUS”).
Product warranty or service will not be extended if: (1) the product is repaired, modied or altered, unless
such repair, modication of alteration is authorized in writing by ASUS; or (2) the serial number of the
product is defaced or missing.
ASUS PROVIDES THIS MANUAL “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OR CONDITIONS OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL ASUS, ITS
DIRECTORS, OFFICERS, EMPLOYEES OR AGENTS BE LIABLE FOR ANY INDIRECT, SPECIAL,
INCIDENTAL, OR CONSEQUENTIAL DAMAGES (INCLUDING DAMAGES FOR LOSS OF PROFITS,
LOSS OF BUSINESS, LOSS OF USE OR DATA, INTERRUPTION OF BUSINESS AND THE LIKE),
EVEN IF ASUS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES ARISING FROM ANY
DEFECT OR ERROR IN THIS MANUAL OR PRODUCT.
SPECIFICATIONS AND INFORMATION CONTAINED IN THIS MANUAL ARE FURNISHED FOR
INFORMATIONAL USE ONLY, AND ARE SUBJECT TO CHANGE AT ANY TIME WITHOUT NOTICE,
AND SHOULD NOT BE CONSTRUED AS A COMMITMENT BY ASUS. ASUS ASSUMES NO
RESPONSIBILITY OR LIABILITY FOR ANY ERRORS OR INACCURACIES THAT MAY APPEAR IN THIS
MANUAL, INCLUDING THE PRODUCTS AND SOFTWARE DESCRIBED IN IT.
Products and corporate names appearing in this manual may or may not be registered trademarks or
copyrights of their respective companies, and are used only for identication or explanation and to the
owners’ benet, without intent to infringe.
E4937
First Edition V1
August 2009

iii
Contents
Notices......................................................................................................... vi
Safety information ..................................................................................... vii
About this guide ....................................................................................... viii
M4A785-M specications summary........................................................... x
Chapter 1: Product introduction
1.1 Welcome! ...................................................................................... 1-1
1.2 Package contents......................................................................... 1-1
1.3 Special features............................................................................ 1-1
1.3.1 Product highlights ........................................................... 1-1
1.3.2 Innovative ASUS features ............................................... 1-3
1.4 Before you proceed ..................................................................... 1-5
1.5 Motherboard overview................................................................. 1-6
1.5.1 Placement direction ........................................................ 1-6
1.5.2 Screw holes .................................................................... 1-6
1.5.3 Motherboard layout ......................................................... 1-7
1.5.4 Layout contents............................................................... 1-7
1.6 Central Processing Unit (CPU) ................................................... 1-8
1.6.1 Installing the CPU ........................................................... 1-8
1.6.2 Installing the heatsink and fan ...................................... 1-10
1.7 System memory ......................................................................... 1-11
1.7.1 Overview ........................................................................1-11
1.7.2 Memory congurations.................................................. 1-12
1.7.3 Installing a DIMM .......................................................... 1-17
1.7.4 Removing a DIMM ........................................................ 1-17
1.8 Expansion slots.......................................................................... 1-18
1.8.1 Installing an expansion card ......................................... 1-18
1.8.2 Conguring an expansion card ..................................... 1-18
1.8.3 PCI slots........................................................................ 1-18
1.8.4 PCI Express x1 slot....................................................... 1-18
1.8.5 PCI Express x16 slot..................................................... 1-18
1.9 Jumpers ...................................................................................... 1-19
1.10 Connectors ................................................................................. 1-20
1.10.1 Rear panel ports ........................................................... 1-20
1.10.2 Internal connectors ....................................................... 1-23

iv
Contents
1.11 Software support........................................................................ 1-30
1.11.1 Installing an operating system ...................................... 1-30
1.11.2 Support DVD information .............................................. 1-30
Chapter 2: BIOS information
2.1 Managing and updating your BIOS ............................................ 2-1
2.1.1 ASUS Update utility ........................................................ 2-1
2.1.2 ASUS EZ Flash 2............................................................ 2-2
2.1.3 ASUS CrashFree BIOS................................................... 2-3
2.2 BIOS setup program .................................................................... 2-4
2.2.1 BIOS menu screen.......................................................... 2-5
2.2.2 Menu bar......................................................................... 2-5
2.2.3 Navigation keys............................................................... 2-5
2.2.4 Menu items ..................................................................... 2-6
2.2.5 Submenu items ............................................................... 2-6
2.2.6 Conguration elds ......................................................... 2-6
2.2.7 Pop-up window ............................................................... 2-6
2.2.8 Scroll bar......................................................................... 2-6
2.2.9 General help ................................................................... 2-6
2.3 Main menu .................................................................................... 2-7
2.3.1 System Time ................................................................... 2-7
2.3.2 System Date ................................................................... 2-7
2.3.3 Primary IDE Master/Slave, SATA 1~6............................. 2-7
2.3.4 SATA Conguration ......................................................... 2-8
2.3.5 System Information ......................................................... 2-9
2.4 Advanced menu ........................................................................... 2-9
2.4.1 JumperFree Conguration .............................................. 2-9
2.4.2 CPU Conguration ........................................................ 2-12
2.4.3 Chipset.......................................................................... 2-13
2.4.4 Onboard Device Conguration...................................... 2-14
2.4.5 PCIPnP ......................................................................... 2-15
2.4.6 USB Conguration ........................................................ 2-15
2.5 Power menu................................................................................ 2-16
2.5.1 Suspend Mode.............................................................. 2-16
2.5.2 ACPI 2.0 Support .......................................................... 2-16

v
Contents
2.5.3 ACPI APIC Support....................................................... 2-16
2.5.4 APM Conguration........................................................ 2-16
2.5.5 HW Monitor Conguration............................................. 2-17
2.5.6 Anti Surgy Support........................................................ 2-17
2.6 Boot menu .................................................................................. 2-18
2.6.1 Boot Device Priority ...................................................... 2-18
2.6.2 Boot Settings Conguration .......................................... 2-18
2.6.3 Security ......................................................................... 2-19
2.7 Tools menu ................................................................................. 2-20
2.7.1 ASUS EZ Flash 2.......................................................... 2-20
2.7.2 Express Gate ................................................................ 2-21
2.7.3 AI NET 2........................................................................ 2-21
2.8 Exit menu.................................................................................... 2-22

vi
Notices
Federal Communications Commission Statement
This device complies with Part 15 of the FCC Rules. Operation is subject to the following two
conditions:
• This device may not cause harmful interference, and
• This device must accept any interference received including interference that may cause
undesired operation.
This equipment has been tested and found to comply with the limits for a Class B digital
device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide
reasonable protection against harmful interference in a residential installation. This
equipment generates, uses and can radiate radio frequency energy and, if not installed
and used in accordance with manufacturer’s instructions, may cause harmful interference
to radio communications. However, there is no guarantee that interference will not occur
in a particular installation. If this equipment does cause harmful interference to radio or
television reception, which can be determined by turning the equipment off and on, the user
is encouraged to try to correct the interference by one or more of the following measures:
• Reorient or relocate the receiving antenna.
• Increase the separation between the equipment and receiver.
• Connect the equipment to an outlet on a circuit different from that to which the receiver is
connected.
• Consult the dealer or an experienced radio/TV technician for help.
The use of shielded cables for connection of the monitor to the graphics card is required
to assure compliance with FCC regulations. Changes or modications to this unit not
expressly approved by the party responsible for compliance could void the user’s authority
to operate this equipment.
Canadian Department of Communications Statement
This digital apparatus does not exceed the Class B limits for radio noise emissions from
digital apparatus set out in the Radio Interference Regulations of the Canadian Department
of Communications.
This class B digital apparatus complies with Canadian ICES-003.
DO NOT throw the motherboard in municipal waste. This product has been designed to
enable proper reuse of parts and recycling. This symbol of the crossed out wheeled bin
indicates that the product (electrical and electronic equipment) should not be placed in
municipal waste. Check local regulations for disposal of electronic products.
DO NOT throw the mercury-containing button cell battery in municipal waste. This symbol
of the crossed out wheeled bin indicates that the battery should not be placed in municipal
waste.
REACH
Complying with the REACH (Registration, Evaluation, Authorisation, and Restriction of
Chemicals) regulatory framework, we published the chemical substances in our products at
ASUS REACH website at http://green.asus.com/english/REACH.htm.

vii
Safety information
Electrical safety
• To prevent electric shock hazard, disconnect the power cable from the electric outlet
before relocating the system.
• When adding or removing devices to or from the system, ensure that the power cables
for the devices are unplugged before the signal cables are connected. If possible,
disconnect all power cables from the existing system before you add a device.
• Before connecting or removing signal cables from the motherboard, ensure that all
power cables are unplugged.
• Seek professional assistance before using an adapter or extension cord. These devices
could interrupt the grounding circuit.
• Ensure that your power supply is set to the correct voltage in your area. If you are not
sure about the voltage of the electrical outlet you are using, contact your local power
company.
• If the power supply is broken, do not try to x it by yourself. Contact a qualied service
technician or your retailer.
• The optical S/PDIF is an optional component (may or may not be included in your
motherboard) and is dened as a CLASS 1 LASER PRODUCT.
INVISIBLE LASER RADIATION, AVOID EXPOSURE TO BEAM.
• Never dispose of the battery in re. It could explode and release harmful substances into
the environment.
• Never dispose of the battery with your regular household waste. Take it to a hazardous
material collection point.
• Never replace the battery with an incorrect battery type.
• RISK OF EXPLOSION IF BATTERY IS REPLACED BY AN INCORRECT TYPE.
• DISPOSE OF USED BATTERIES ACCORDING TO THE ABOVE BATTERY-RELATED
INSTRUCTIONS.

viii
About this guide
This user guide contains the information you need when installing and conguring the
motherboard.
How this guide is organized
This guide contains the following parts:
• Chapter 1: Product introduction
This chapter describes the features of the motherboard and the new technology it
supports.
• Chapter 2: BIOS information
This chapter tells how to change system settings through the BIOS Setup menus.
Detailed descriptions of the BIOS parameters are also provided.
Operation safety
• Before installing the motherboard and adding devices on it, carefully read all the manuals
that came with the package.
• Before using the product, ensure that all cables are correctly connected and the power
cables are not damaged. If you detect any damage, contact your dealer immediately.
• To avoid short circuits, keep paper clips, screws, and staples away from connectors,
slots, sockets and circuitry.
• Avoid dust, humidity, and temperature extremes. Do not place the product in any area
where it may become wet.
• Place the product on a stable surface.
• If you encounter technical problems with the product, contact a qualied service
technician or your retailer.
This motherboard should only be used in environments with ambient temperatures between
5ºC (41ºF) and 40ºC (104ºF).

ix
Conventions used in this guide
To ensure that you perform certain tasks properly, take note of the following symbols used
throughout this manual.
DANGER/WARNING:Information to prevent injury to yourself when trying to
complete a task.
CAUTION: Information to prevent damage to the components when trying to
complete a task.
NOTE: Tips and additional information to help you complete a task.
IMPORTANT: Instructions that you MUST follow to complete a task.
Where to nd more information
Refer to the following sources for additional information and for product and software
updates.
1. ASUS websites
The ASUS website provides updated information on ASUS hardware and software
products. Refer to the ASUS contact information.
2. Optional documentation
Your product package may include optional documentation, such as warranty yers,
that may have been added by your dealer. These documents are not part of the
standard package.
Typography
Bold text Indicates a menu or an item to select.
Italics Used to emphasize a word or a phrase.
<Key> Keys enclosed in the less-than and greater-than sign means
that you must press the enclosed key.
Example: <Enter> means that you must press the Enter or
Return key.
<Key1>+<Key2>+<Key3> If you must press two or more keys simultaneously, the key
names are linked with a plus sign (+).
Example: <Ctrl>+<Alt>+<D>

x
M4A785-M specications summary
(continued on the next page)
CPU AMD® Phenom™ II / Athlon™ II / Phenom™ / Athlon™ / Sempron™
family processors (AM3 / AM2+ / AM2)
Supports 45nm CPU
Supports CPU up to 125W
AMD® Cool ‘n’ Quiet™ 2.0 technology (depending on CPU type)
* Refer to www.asus.com for the AMD®CPU support list.
Chipset AMD® 785G / SB710
Front Side Bus Up to 5200MT/s HyperTransport™ 3.0 interface for AM2+ /AM3 CPU
2000 / 1600 MT/s for AM2 CPU
Memory Dual-channel memory architecture
4 x 240-pin DIMM slots support maximum 16GB unbuffered ECC
and non-ECC DDR2 1200(O.C.)/1066/800/667MHz memory
modules
* We recommend that you install the DDR2 1200(O.C.) DIMMs on
the blue slots for better performance.
** DDR2 1200(O.C.)/1066 is supported by AM3/AM2+ CPU only.
*** Due to AM3/AM2+ CPU limitation, only one DDR2
1200(O.C.)/1066 is supported per channel.
****Refer to www.asus.com for the latest Memory QVL
(Qualied Vendors List).
***** When you install a total memory of 4GB or more, Windows®
32-bit operating system may only recognize less than 3GB. We
recommend a maximum of 3GB system memory if you are using
a Windows® 32-bit operating system.
Graphics Integrated ATI Radeon™ HD 4200 GPU
Maximum shared memory up to 512MB
Supports DVI-D with HDCP compliant with max. resolution up to
2560x1600 (@60Hz Dual-link)
Supports HDMI™ technology with max. resolution up to
1920x1200 (1080P) @60Hz
Supports RGB with max. resolution up to 2048x1536 (@85Hz)
Supports Hybrid CrossFireX™ (for Windows® Vista only)
Supports Microsoft® DirectX 10.1, OpenGL 2.0, Shader Model 4.1,
Hardware Decode Acceleration for H.264, VC-1, and MPEG-2
Dual VGA output supports:
– RGB & DVI
– RGB & HDMI
* Refer to www.amd.com for the discrete GPUs which support Hybrid
CrossFireX™.
Expansion slots 1 x PCIe 2.0 x16 slot
1 x PCIe x1 slot
2 x PCI 2.2 slots

xi
M4A785-M specications summary
Storage 1 x Ultra DMA 133/100/66 connector for up to 2 PATA devices
6 x Serial ATA 3Gb/s connectors support RAID 0, RAID 1,
RAID 0+1, and JBOD congurations
Audio VIA® VT1708S 8-channel High Denition Audio CODEC
– Optical S/PDIF out port at back I/O
– Supports Jack-detection, Multi-streaming, and Front Panel
Jack-Retasking
USB Supports up to 12 USB 2.0/1.1 ports (6 ports at mid-board, 6 ports at
the back panel)
LAN Realtek® 8112L PCIe Gigabit LAN controller
ASUS unique
features
ASUS 4+1 Phase Power Design
ASUS EPU-4 Engine
ASUS Express Gate
ASUS Turbo Key
ASUS Anti-Surge
ASUS CrashFree BIOS 3
ASUS EZ Flash 2
ASUS Q-Fan
ASUS MyLogo 2
ASUS AI NET 2
ASUS
overclocking
features
Intelligent overclocking tools:
– Turbo Key
– GPU NOS
* GPU NOS is not supported in Hybrid CrossFireX™ mode.
SFS (Stepless Frequency Selection):
– FSB tuning from 200MHz up to 550MHz at 1MHz increment
– PCIe frequency tuning from 100MHz up to 150MHz at 1MHz
increment
Overclocking Protection:
ASUS C.P.R. (CPU Parameter Recall)
Back panel I/O
ports
1 x PS/2 Keyboard/Mouse Combo port
1 x Optical S/PDIF Out port
1 x VGA port
1 x DVI port
1 x HDMI port
1 x LAN (RJ-45) port
6 x USB 2.0/1.1 ports
8-channel audio I/O ports
(continued on the next page)

xii
* Specications are subject to change without notice.
M4A785-M specications summary
Internal I/O connectors 3 x USB 2.0/1.1 connectors support additional
6 USB 2.0/1.1 ports
1 x IDE connector
1 x COM connector
1 x LPT connector
6 x SATA connectors
1 x Front panel audio connector
1 x System panel connector
1 x S/PDIF Out connector
1 x CPU fan connector
1 x Chassis fan connector
1 x 24-pin EATX power connector
1 x 4-pin ATX 12V power connector
BIOS 8Mb Flash ROM, AMI BIOS, PnP, DMI v2.0, WfM2.0,
SM BIOS v2.5, ACPI v2.0a,
Accessories 1 x Ultra DMA 133/100/66 cable
2 x Serial ATA cables
1 x I/O shield
1 x User Manual
Support DVD Drivers
ASUS Update
ASUS PC Probe II
Anti-Virus software (OEM version)
Form factor MicroATX form factor: 9.6 in x 9.6 in (24.4 cm x 24.4 cm)

1.2 Package contents
Check your motherboard package for the following items.
Motherboard ASUS M4A785-M motherboard
Cables 2 x Serial ATA cables
1 x Ultra DMA 133/100/66 cable
Accessories 1 x I/O shield
Application DVD ASUS motherboard Support DVD
Documentations User Manual
If any of the above items is damaged or missing, contact your retailer.
Chapter 1
Product introduction
1.3 Special features
1.3.1 Product highlights
1.1 Welcome!
Thank you for buying an ASUS®M4A785-M motherboard!
The motherboard delivers a host of new features and latest technologies, making it another
standout in the long line of ASUS quality motherboards!
Before you start installing the motherboard, and hardware devices on it, check the items in
your package with the list below.
AMD®Phenom™ II / Athlon™II / Sempron™ 100 Series
processors
This motherboard supports AMD®AM3 multi-core processors with unique
L3 cache and delivers better overclocking capabilities with less power
consumption. It features dual-channel DDR2 1066 memory support and
accelerates data transfer rate up to 5200MT/s via HyperTransport™ 3.0
based system bus. This motherboard also supports AMD®CPUs in the
new 45nm manufacturing process.
ASUS M4A785-M 1-1

AMD®Phenom™ X4 / Phenom™ X3 / Athlon™ X2 / Athlon™ /
Sempron™ processors (socket AM2+/AM2)
This motherboard supports AMD® Socket AM2+ multi-core processors.
It features dual-channel DDR2 1066 memory support, data transfer rate
up to 5200MT/s via HyperTransport™ 3.0 based system bus, and AMD®
Cool ‘n’ Quiet™ Technology.
AMD®785G Chipset
The AMD® 785G Chipset is designed to support up to 5200MT/s
HyperTransport™ 3.0 (HT 3.0) interface speed and PCI Express 2.0
x16 graphics. It is optimized with AMD’s latest AM3 multi-core CPUs to
provide excellent system performance and overclocking capabilities.
HyperTransport™ 3.0 support
HyperTransport™ 3.0 technology provides 2.6 times more bandwidth
than HT1.0 that radically improves system efciency for a smoother and
faster computing environment.
AMD Cool ‘n’ Quiet Technology
This motherboard supports the AMD Cool ‘n’ Quiet technology which
monitors system operation and automatically adjusts CPU voltage and
frequency for a cool and quiet operating environment.
DDR2 1200 (O.C.)
This motherboard supports DDR2 1200 (O.C.) that provides faster
data transfer rate and more bandwidth to increase memory computing
efciency, enhancing system performance in 3D graphics and other
memory demanding applications.
S/PDIF digital sound ready
This motherboard provides convenient connectivity to external home
theater audio systems via coaxial and optical S/PDIF_OUT (SONY-
PHILIPS Digital Interface) jacks. The S/PDIF transfers digital audio
without converting it to analog format and keeps the best signal quality.
Hybrid CrossFireX™ support
ATI Hybrid CrossFireX™ technology greatly boosts graphics performance
with an onboard GPU and a discrete GPU.
• Hybrid CrossFireX™ is supported by Windows®Vista OS only.
• Refer to www.amd.com for the discrete GPUs which support Hybrid CrossFireX™.
Chapter 1: Product introduction1-2

Serial ATA 3Gb/s technology
This motherboard supports hard drives based on the Serial ATA (SATA)
3Gb/s storage specications, delivering enhanced salability and doubling
the bus bandwidth for high-speed data saving and retrieval.
8-channel high denition audio
The onboard 8-channel HD audio (High Denition Audio, previously
codenamed Azalia) CODEC enables high-quality 192KHz/24-bit audio
output and jack-detect feature that automatically detects and identies
what types of peripherals are plugged into the audio I/O jacks and noties
users of inappropriate connection, which means there will be no more
confusion of Line-in, Line-out, and Mic jacks.
Gigabit LAN solution
The onboard LAN controller is a highly integrated Gb LAN controller. It is
enhanced with an ACPI management function to provide efcient power
management for advanced operating systems.
HDMI support
HDMI (High-Denition Multimedia Interface) is a set of digital video
standards that deliver multi-channel digital audio and uncompressed
digital video for full HD 1080p visuals through a single cable. Supporting
HDCP copy protection such as HD DVD and Blu-ray discs, HDMI
provides you with the highest-quality home theater experience.
HDMI/DVI/RGB support
This motherboard supports multiple digital and analog display output
interfaces: HDMI, DVI, and D-Sub. With such diversity of display outputs,
you are able to choose and upgrade display devices freely.
1.3.2 Innovative ASUS features
ASUS Express Gate
ASUS Express Gate is an instant-on environment that gives you quick
access to the Internet. Five seconds after powering on your computer,
you can instantly surf the Internet without entering the Windows®OS.
• ASUS Express Gate supports installation on SATA HDDs, USB HDDs and ash
drives with at least 1.2GB free disk space. When installing it on USB HDDs or
ash drives, connect the drives to the motherboard USB port before turning on the
computer.
• The actual boot time depends on the system conguration.
• ASUS Express Gate supports le uploading from SATA HDDs, ODDs and USB
drives. It supports le downloading to USB drives only.
• ASUS Express Gate complies with the OpenGL standard. Refer to support.asus.com
for Express Gate source codes.
ASUS M4A785-M 1-3

ASUS CrashFree BIOS 3
ASUS CrashFree BIOS 3 is an auto-recovery tool that allows you to
restore a corrupted BIOS le using the bundled support DVD or a USB
ash disk that contains the BIOS le.
ASUS EZ Flash 2
ASUS EZ Flash 2 allows you to update the BIOS from a USB ash disk
before entering the OS.
ASUS EPU
ASUS EPU is a unique power saving technology that detects the current
system loadings and adjusts the power consumption in real time.
ASUS Turbo Key
ASUS Turbo Key allows you to turn the PC power button into
an overclocking button. After the easy setup, Turbo Key boosts
performances without interrupting ongoing work or games, simply through
pressing the button.
ASUS Anti-Surge Protection
This special design prevents expensive devices and the motherboard
from damage caused by power surges from switching power supply unit
(PSU).
GPU NOS
GPU NOS technology intelligently detects graphic loading and
automatically boosts performance for the most demanding tasks.
It provides you with a faster reaction time for an excellent graphics
performance.
GPU NOS is not supported in Hybrid CrossFireX™ mode.
ASUS MyLogo 2™
Turn your favorite photos into 256-color boot logos to personalize your
system.
ASUS Q-Fan
ASUS Q-Fan technology intelligently adjusts CPU fan speeds according
to system loading to ensure a quiet, cool, and efcient operation.
ASUS AI NET 2
ASUS AI NET 2 remotely detects the cable connection immediately after
you turn on the system and any faulty cable connections are reported
back up to 100 meters at 1 meter accuracy.
Chapter 1: Product introduction1-4

C.P.R. (CPU Parameter Recall)
The BIOS C.P.R. feature automatically restores the CPU default settings
when the system hangs due to overclocking failure. C.P.R. eliminates the
need to open the system chassis and clear the RTC data. Simply shut
down and reboot the system, and the BIOS automatically restores the
CPU parameters to their default settings.
Green ASUS
This motherboard and its packaging comply with the European Union’s
Restriction on the use of Hazardous Substances (RoHS). This is in line
with the ASUS vision of creating environment-friendly and recyclable
products/packaging to safeguard consumers’ health while minimizing the
impact on the environment.
1.4 Before you proceed
Take note of the following precautions before you install motherboard components or change
any motherboard settings.
• Unplug the power cord from the wall socket before touching any component.
• Before handling components, use a grounded wrist strap or touch a safely grounded
object or a metal object, such as the power supply case, to avoid damaging them due to
static electricity.
• Hold components by the edges to avoid touching the ICs on them.
• Whenever you uninstall any component, place it on a grounded antistatic pad or in the
bag that came with the component.
• Before you install or remove any component, switch off the ATX power supply and
detach its power cord. Failure to do so may cause severe damage to the motherboard,
peripherals, or components.
Onboard LED
The motherboard comes with a standby power LED that lights up to indicate that the system
is ON, in sleep mode, or in soft-off mode. This is a reminder that you should shut down
the system and unplug the power cable before removing or plugging in any motherboard
component. The illustration below shows the location of the onboard LED.
ASUS M4A785-M 1-5

1.5 Motherboard overview
1.5.1 Placement direction
When installing the motherboard, ensure that you place it into the chassis in the correct
orientation. The edge with external ports goes to the rear part of the chassis as indicated in
the image below.
DO NOT overtighten the screws! Doing so can damage the motherboard.
Place this side towards
the rear of the chassis.
1.5.2 Screw holes
Place eight screws into the holes indicated by circles to secure the motherboard to the
chassis.
Chapter 1: Product introduction1-6

1.5.3 Motherboard layout
1.5.4 Layout contents
Connectors/Jumpers/Slots/LED Page Connectors/Jumpers/Slots/LED Page
1. CPU and chassis fan connectors
(4-pin CPU_FAN and 3-pin CHA_FAN)
1-29 8. Clear RTC RAM (3-pin CLRTC) 1-19
2. ATX power connectors (24-pin EATXPWR,
4-pin ATX12V)
1-23 9. SATA connectors (7-pin SATA1-6) 1-25
3. CPU Socket AM2+ 1-8 10. System panel connector (20-8 pin PANEL) 1-26
4. DDR2 DIMM slots 1-11 11. Onboard power LED (SB_PWR)
5. Serial port connector (10-1 pin COM1) 1-27 12. USB connectors (10-1 pin USB78, USB910,
USB1112)
1-27
6. LPT connector (26-1 pin LPT) 1-29 13. Digital audio connector (4-1 pin SPDIF_OUT) 1-28
7. IDE connector (40-1 pin PRI_IDE) 1-24 14. Front panel audio connector (10-1 pin AAFP) 1-28
ASUS M4A785-M 1-7

1.6 Central Processing Unit (CPU)
The motherboard comes with an AM2+/AM2 socket designed for Phenom™ II /
Athlon™ II / Phenom™ / Athlon™/ Sempron™ family processors (AM3/AM2+/AM2).
1.6.1 Installing the CPU
To install a CPU:
1. Locate the CPU socket on the motherboard.
2. Press the lever sideways to unlock the
socket, then lift it up to a 90°-100° angle.
Socket lever
Ensure that the socket lever is lifted up to a 90°-100° angle; otherwise, the CPU will not t
in completely.
3. Position the CPU above the socket such that the CPU
corner with the gold triangle matches the socket corner
with a small triangle.
4. Carefully insert the CPU into the socket until it ts in place.
The CPU ts only in one correct orientation.
DO NOT force the CPU into the socket to
prevent bending the pins and damaging the
CPU!
Gold triangle
Small triangle
The AM2/AM2+ socket has a different pinout from the 940-pin socket designed for the AMD
Opteron™ processor. Use a CPU that is designed for the AM2/AM2+ socket.
Chapter 1: Product introduction1-8