Asus M3N78-CM User manual

Motherboard
M3N78-CM

ii
Copyright © 2008 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.
E4309
Second Edition V2
November 2008

iii
Contents
Notices......................................................................................................... vi
Safety information ..................................................................................... vii
About this guide ........................................................................................ vii
M3N78-CM specications summary ......................................................... ix
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 ..................................................................... 1-4
1.5 Motherboard overview................................................................. 1-5
1.5.1 Placement direction ........................................................ 1-5
1.5.2 Screw holes .................................................................... 1-5
1.5.3 Motherboard layout ......................................................... 1-6
1.5.4 Layout contents............................................................... 1-7
1.6 Central Processing Unit (CPU) ................................................... 1-7
1.6.1 Installing the CPU ........................................................... 1-7
1.6.2 Installing the heatsink and fan ........................................ 1-9
1.7 System memory ......................................................................... 1-10
1.7.1 Overview ....................................................................... 1-10
1.7.2 Memory congurations...................................................1-11
1.7.3 Installing a DIMM .......................................................... 1-14
1.7.4 Removing a DIMM ........................................................ 1-14
1.8 Expansion slots.......................................................................... 1-15
1.8.1 Installing an expansion card ......................................... 1-15
1.8.2 Conguring an expansion card ..................................... 1-15
1.8.4 PCI slots........................................................................ 1-15
1.8.5 PCI Express x1 slots..................................................... 1-15
1.8.6 PCI Express x16 slot..................................................... 1-15
1.9 Jumpers ...................................................................................... 1-16
1.10 Connectors ................................................................................. 1-17
1.10.1 Rear panel connectors.................................................. 1-17

iv
Contents
1.10.2 Internal connectors ....................................................... 1-18
1.11 Software support........................................................................ 1-26
1.11.1 Installing an operating system ...................................... 1-26
1.11.2 Support DVD information .............................................. 1-26
Chapter 2: BIOS information
2.1 Managing and updating your BIOS ............................................ 2-1
2.1.1 ASUS Update utility ........................................................ 2-1
2.1.2 Creating a bootable oppy disk....................................... 2-2
2.1.3 ASUS EZ Flash 2 utility................................................... 2-3
2.1.4 AFUDOS utility................................................................ 2-4
2.1.5 ASUS CrashFree BIOS 3 utility ...................................... 2-5
2.2 BIOS setup program .................................................................... 2-7
2.2.1 BIOS menu screen.......................................................... 2-8
2.2.2 Menu bar......................................................................... 2-8
2.2.3 Navigation keys............................................................... 2-9
2.2.4 Menu items ..................................................................... 2-9
2.2.5 Sub-menu items.............................................................. 2-9
2.2.6 Conguration elds ......................................................... 2-9
2.2.7 General help ................................................................... 2-9
2.2.8 Pop-up window ............................................................... 2-9
2.2.9 Scroll bar......................................................................... 2-9
2.3 Main menu .................................................................................. 2-10
2.3.1 System Time ................................................................. 2-10
2.3.2 System Date ................................................................. 2-10
2.3.3 Legacy Diskette A ......................................................... 2-10
2.3.4 Primary IDE Master/Slave, SATA1~4............................ 2-10
2.3.5 Storage Conguration ....................................................2-11
2.3.6 System Information ........................................................2-11
2.4 Advanced menu ......................................................................... 2-12
2.4.1 JumperFree Conguration ............................................ 2-12
2.4.2 CPU Conguration ........................................................ 2-15
2.4.3 Chipset.......................................................................... 2-15
2.4.4 Onboard Devices Conguration.................................... 2-17
2.4.5 PCI PnP ........................................................................ 2-17
2.4.6 USB Conguration ........................................................ 2-18

v
Contents
2.5 Power menu................................................................................ 2-19
2.5.1 Suspend Mode.............................................................. 2-19
2.5.2 ACPI
2.0 Support ......................................................... 2-19
2.5.3 ACPI APIC Support....................................................... 2-19
2.5.4 APM Conguration........................................................ 2-19
2.5.5 Hardware Monitor ......................................................... 2-20
2.6 Boot menu .................................................................................. 2-21
2.6.1 Boot Device Priority ...................................................... 2-21
2.6.2 Boot Settings Conguration .......................................... 2-21
2.6.3 Security ......................................................................... 2-22
2.7 Tools menu ................................................................................. 2-23
2.7.1 ASUS EZ Flash 2.......................................................... 2-23
2.7.2 Express Gate ................................................................ 2-24
2.8 Exit menu.................................................................................... 2-25

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.

vii
Safety information
Electrical safety
• To prevent electrical shock hazard, disconnect the power cable from the electrical 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.
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.
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 setup
This chapter tells how to change system settings through the BIOS Setup menus.
Detailed descriptions of the BIOS parameters are also provided.

viii
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>
Command Means that you must type the command exactly as shown,
then supply the required item or value enclosed in
brackets.
Example: At the DOS prompt, type the command line:
afudos /i[lename]
afudos /iM3N78CM.ROM

ix
CPU AMD socket AM2+ / AM2 for AMD Phenom™FX /
Phenom™ / Athlon™ / SempronTM processors
AMD64 architecture enables simultaneous 32-bit and
64-bit computing
Supports AMD Cool ‘n’ Quiet™ Technology
Support CPU up to 140W
Chipset NVIDIA®GeForce® 8200 (MCP78S)
System bus Up to 5200 MT/s HyperTransport™ 3.0 interface for
AM2+ CPU; 2000/1600 MT/s for AM2 CPU
Memory Dual-channel memory architecture 4 x 240-pin DIMM
sockets support up to 8 GB of unbufferred ECC and
non-ECC 1066 / 800 / 667 / 533 MHz DDR2 memory
modules
Notes:
• Due to AMD CPU limitation, DDR2 1066 is supported by AM2+
CPU for one DIMM per channel only.
• When installing total memory of 4GB capacity or more,
Windows® 32-bit operation system may only recognize less
than 3GB. Hence, a total installed memory of less than 3GB is
recommended.
• Refer to www.asus.com for the memory QVL (Qualied Vendors
List.)
Expansion slots 1 x PCI Express™ x16 slot
1 x PCIe x 1 slot
2 x PCI slots
Storage Southbridge
- 1 x Ultra DMA 133 / 100 interface
- 6 x Serial ATA 3 Gb/s hard disk drives supporting
RAID 0, RAID 1, RAID 5, RAID 0+1, and JBOD
conguration
High Denition Audio VT1708B High Denition Audio 8-channel CODEC
Supports S/PDIF out interface, Jack-detect and multi-
streaming
USB Supports up to 10 USB 2.0/1.1 ports (6 ports
at mid-board, 4 ports at back panel)
LAN NVIDIA® nForce built-in Gigabit MAC with external
Realtek8211CL PHY
BIOS 8 Mb Flash ROM, AMI BIOS, PnP, DMI2.0, WfM2.0,
SM BIOS 2.5, ACPI 2.0a
ASUS Overclocking
Features
Precision Tweaker:
- vDIMM: 8-step DRAM voltage control
Stepless Frequency Selection (SFS):
- SB tuning up to 300MHz at 1MHz increment
Overclocking Protection:
- ASUS CPU Parameter Recall (C.P.R.)
M3N78-CM specications summary
(continued on the next page)

x
M3N78-CM specications summary
Back panel I/O ports 1 x LAN (RJ-45) port
1 x COM port
1 x DVI port
6 x USB 2.0 / 1.1 ports
1 x VGA Out port
1 x PS/2 keyboard port
8-channel audio ports
Internal I/O connectors 1 x High Denition front panel audio connector
1 x IDE connector
1 x Floppy disk drive connector
1 x CD audio-in connector
1 x CPU fan connector
1 x Chassis fan connector
1 x LPT connector
6 x SATA connectors
1 x S/PDIF Out connector
3 x USB 2.0 connectors for 6 additional USB 2.0 ports
1 x 24-pin EATX power connector
1 x 4-pin x ATX 12V power connector
1 x System panel connector
ASUS Unique Features ASUS Express Gate:
- Access the Internet in 5-second* boot time without
entering Windows
- A built-in OS offers instant fun platform for Internet
and Instant Messenger
* The actual boot time depends on the system conguration.
ASUS Quiet Thernal Solution:
- ASUS Q-Fan
ASUS EZ DIY:
- ASUS CrashFree BIOS 3
- ASUS EZ Flash 2
Other Feature:
- ASUS MyLogo 2™
- AI NET 2
Accessories 2 x SATA cables
2 x power cables
1 x UltraDMA 133 / 100 / 66 cable
1 x Floppy Disk Drive cable
1 x I/O Shield
User’s manual
Form Factor MicroATX: 9.6 in. x 9.6 in. (24.4 cm x 24.4 cm)
Support DVD Device drivers
Express Gate
ASUS PC Probe II
ASUS Update utility
Anti-virus software (OEM version)
*Specications are subject to change without notice.

1.1 Welcome!
Thank you for buying an ASUS® M3N78-CM 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.
1.2 Package contents
Check your motherboard package for the following items.
Motherboard ASUS M3N78-CM motherboard
Cables 2 x Serial ATA cables
2 x power cables
1 x Ultra DMA 133 / 100 cable
1 x Floppy disk drive cable
Accessories 1 x I/O shield
Application DVD ASUS motherboard support DVD
Documentation User guide
If any of the above items is damaged or missing, contact your retailer.
1.3 Special features
1.3.1 Product highlights
AMD socket AM2+ Phenom FX / Phenom
The motherboard supports AMD socket AM2+ multi-core processors. It features dual-
channel DDR2 1066 memory support and accelerates data transfer rate up to 5200 MT/s via
HyperTransport 3.0 based system bus. See page 1-7 for details.
AMD socket AM2 Athlon 64 /
Athlon 64 X2 / Athlon 64 FX / Sempron
The motherboard supports AMD socket AM2 Athlon 64 / Athlon 64 X2 / Athlon 64 FX
/ Sempron processors with 2MB / 1MB / 512KB L2 cache, which is based on 64-bit
architecture. It features 2000 / 1600 MT/s HyperTransport System Bus, dual-channel
un-buffered DDR2 memory support and AMD Cool ‘n’ Quiet Technology. See page 1-7 for
details.
Chapter 1
Product introduction
Chapter 1: Product introduction 1-1

AMD Cool ‘n’ Quiet Technology
The 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.
Dual channel DDR2 1066 support
This motherboard supports DDR2 1066. It provides faster data transfer rate and more
bandwidth to increase memory data transfer rate and computing efciency, enhancing system
performance in 3D graphics and other memory demanding applications. See pages 1-10 for
details.
DDR2 1066 is for AM2+ only.
Gigabit LAN solution
Gigabit LAN is the networking standard for the early future and is ideal for handling large
amounts of data such as video, audio, and voice. See page 1-17 for details.
Serial ATA 3Gb/s technology
The motherboard supports next-generation SATA hard drives based on the new SATA 3Gb/s
storage specication.
High Denition Audio
Enjoy high-end sound quality on your PC! The onboard 8-channel HD audio (High Denition
Audio, previously codenamed Azalia) CODEC enables high-quality 192KHz / 24-bit audio
output, jack-detect feature.
64-bit CPU support
64-bit computing, the technology to replace 32-bit architecture, delivers advanced system
performance, faster memory access and increased productivity. This motherboard provides
excellent compatibility and exibility by supporting either 64-bit or 32-bit architecture.
DVITM Interface
DVI (Digital Visual Interface) provides high visual quality of digital display devices such as
LCD monitor. The interface of this motherboard is HDCP compliant, allowing playback of HD
DVD, Blu-ray Disc and other protected content.
HyperTransportTM 3.0 support
HyperTransportTM 3.0 technology provides 2.6 times more bandwith than HyperTransportTM
1.0, radically improving system efciency to create a smoother, faster computing
environment.
1-2 ASUS M3N78-CM

NVIDIA®GeForce®8200
The NVIDIA®GeForce® 8200 offers the lastest support of Hybrid SLI technology,
DirectX10 graphics features, HD video playback with HDMI / DVI output. It also supports
HyperTransport TM 3.0 interface, PCI ExpressTM 2.0 bus architecture, Serial ATA 3 GB/s
devices, and is optimized with AMD’s latest AM2+ and multi-core CPUs to provide excellent
system performance.
Hybrid SLITM
Hybrid SLITM technology is a unique hybrid multi-GPU technology built upon NVIDIA. Hybrid
SLI technology today includes two primary feaures: GeForce Boost and HybridPowerTM.
GeForce Boost turbo-charges performance of NVIDIA descrete graphics cards when
combined with this series motherboard GPUs. HybridPowerTM unleashed graphics
performance when needed and enabled discrete GeForce GPU(s) to the motherboard GPU
for a quiet, low power PC experience.
PCI Express 2.0 support
The motherboard supports the latest PCI Express 2.0 devices for double speed and
bandwidth which enhances system performance.See page 1-15 for details.
1.3.2 Innovative ASUS features
ASUS MyLogo2™
Turn your favorite photos into 256-color boot logos to personalize your system. See page
2-21 for details.
ASUS CrashFree BIOS 3
The ASUS CrashFree BIOS 3 allows users to restore corrupted BIOS data from a USB
ash disk containing the BIOS le. This utility saves users the cost and hassle of buying a
replacement BIOS chip. See page 2-5 for details.
ASUS EZ Flash 2
EZ Flash 2 is a user-friendly BIOS update utility. Simply launch this tool and update BIOS
from a USB ash disk before entering the OS. You can update your BIOS only in a few clicks
without preparing an additional oppy diskette or using an OS-based ash utility. See page
2-3 for details.
ASUS Q-Fan
ASUS Q-Fan technology intelligently adjusts CPU fan speeds according to system loading to
ensure quiet, cool and efcient operation.
Visit the ASUS website (www.asus.com) to download the lastest Hybrid SLI driver after
NVIDIA get the Hybrid SLI function prepared.
Chapter 1: Product introduction 1-3

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.
• Use a grounded wrist strap or touch a safely grounded object or a metal object, such
as the power supply case, before handling components 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, ensure that the ATX power supply is
switched off or the power cord is detached from the power supply. Failure to do so may
cause severe damage to the motherboard, peripherals, or components.
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.
C.P.R. (CPU Parameter Recall)
The C.P.R. feature of the motherboard BIOS allows automatic re-setting to the BIOS default
settings in case the system hangs due to overclocking. When the system hangs due to
overclocking, 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
default setting for each parameter.
Express Gate
Taking only 5 seconds to go online from bootup, Express Gate is the one-stop gateway to
instant fun! It’s a unique motherboard built-in OS. You can utilize the most popular Instant
Messengers (IM) like MSN, Skype, Google talk, QQ, and Yahoo! Messenger to keep in touch
with friends, or quickly check on the weather and e-mails just before leaving your house.
What’s more, the user-friendly picture manager lets you view your pictures without entering
Windows at anytime!
• The actual boot time depends on the system conguration.
• ASUS Express Gate supports le uploading from SATA HDDs, ODDs and USB drive and
downloading to USB drives only.
1-4 ASUS M3N78-CM

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.
1.5.2 Screw holes
Place eight (8) screws into the holes indicated by circles to secure the motherboard to the
chassis.
Do not overtighten the screws! Doing so can damage the motherboard.
Place this side towards
the rear of the chassis.
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.
M3N78-CM
R
M3N78-CM Onboard LED
SB_PWR
ON
Standby
Power
OFF
Powered
Off
M3N78-CM
Chapter 1: Product introduction 1-5

1 43
1
2
6
78
5
910111213141516
1.5.3 Motherboard layout
Refer to 1.10 Connectors for more information about rear panel connectors and internal
connectors.
1-6 ASUS M3N78-CM

1.5.4 Layout contents
Connectors/Jumpers/Slots Page
1. ATX power connectors (24-pin EATXPWR, 8-pin ATX12V) 1-23
2. AMD CPU 940-pin Socket 1-7
3. CPU fan connector (4-pin CPU_FAN) 1-8
4. DDR2 DIMM slots 1-10
5. Serial ATA connectors (7-pin SATA1-6) 1-21
6. IDE connector (40-1 pin PRI_EIDE) 1-20
7. USB connectors (10-1 pin USB78, USB910, USB1112) 1-22
8. LPT connector 1-19
9. Clear RTC RAM (3-pin CLRTC) 1-16
10. Onboard LED 1-5
11. System panel connector (20-8 pin PANEL) 1-25
12. Floppy disk drive connector (34-1 pin FLOPPY) 1-18
13. Front panel audio connector (10-1 pin AAFP) 1-22
14. Optical drive audio connector (4-pin CD) 1-20
15. Digital audio connector (4-1 pin SPDIF_OUT) 1-19
16. Chassis and power fan connectors (3-pin CHA_FAN, 3-pin PWR_FAN) 1-24
1.6 Central Processing Unit (CPU)
The motherboard comes with an AM2+ / AM2 socket designed for AMD® AM2+ / AM2
Phenom™ FX / Phenom / Athlon™ / Sempron™ processor.
The AM2/AM2+ socket has a different pinout from the 940-pin socket designed for the
AMD Opteron™ processor. Ensure that you use a CPU that is designed for the AM2/AM2+
socket. The CPU ts in only one correct orientation. DO NOT force the CPU into the socket
to prevent bending the connectors on the socket and damaging the CPU!
1.6.1 Installing the CPU
To install a CPU:
1. Locate the CPU socket on the motherboard.
M3N78-CM
R
M3N78-CM CPU Socket AM2+
Chapter 1: Product introduction 1-7

2. Unlock the socket by pressing the lever sideways, then lift it
up to a 90°-100° angle. Socket lever
Ensure that the socket lever is lifted up to 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
5. When the CPU is in place, push down the socket
lever to secure the CPU. The lever clicks on the side
tab to indicate that it is locked.
6. Install a CPU heatsink and fan following the
instructions that came with the heatsink package.
You can also refer to section 1.6.2 Installing
heatsink and fan for instructions.
7. Connect the CPU fan cable to the CPU_FAN connector on the motherboard.
Do not forget to connect the CPU
fan connector! Hardware monitoring
errors can occur if you fail to plug
this connector.
M3N78-CM
R
M3N78-CM CPU Fan Connector
CPU_FAN
GND
CPU FAN PWR
CPU FAN IN
CPU FAN PWM
1-8 ASUS M3N78-CM

1.6.2 Installing the heatsink and fan
Make sure that you use only AMD-certied heatsink and fan assembly.
Follow these steps to install the CPU heatsink and fan.
1. Place the heatsink on top of the installed CPU, making sure that the heatsink ts
properly on the retention module base.
• The retention module base is already installed on the motherboard upon purchase.
• You do not have to remove the retention module base when installing the CPU or
installing other motherboard components.
• If you purchased a separate CPU heatsink and fan assembly, make sure that a Thermal
Interface Material is properly applied to the CPU heatsink or CPU before you install the
heatsink and fan assembly.
CPU Fan
CPU Heatsink
Retention bracket
Retention bracket lock
Retention Module Base
Your boxed CPU heatsink and fan assembly should come with installation instructions for
the CPU, heatsink, and the retention mechanism. If the instructions in this section do not
match the CPU documentation, follow the latter.
2. Attach one end of the retention bracket to the retention module base.
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Chapter 1: Product introduction 1-9

3. Align the other end of the retention bracket (near the retention bracket lock) to the
retention module base. A clicking sound denotes that the retention bracket is in place.
Make sure that the fan and heatsink assembly perfectly ts the retention mechanism
module base, otherwise you cannot snap the retention bracket in place.
4. Push down the retention bracket lock on the retention mechanism to secure the
heatsink and fan to the module base.
5. When the fan and heatsink assembly is in place, connect the CPU fan cable to the
connector on the motherboard labeled CPU_FAN.
Do not forget to connect the CPU fan connector! Hardware monitoring errors can occur if
you fail to plug this connector.
1.7 System memory
1.7.1 Overview
The motherboard comes with four Double Data Rate 2 (DDR2) Dual Inline Memory Modules
(DIMM) sockets.
A DDR2 module has the same physical dimensions as a DDR DIMM but has a 240-pin
footprint compared to the 184-pin DDR DIMM. DDR2 DIMMs are notched differently to
prevent installation on a DDR DIMM socket.
The gure illustrates the location of the DDR2 DIMM sockets:
M3N78-CM
R
M3N78-CM 240-pin DDR2 DIMM Sockets
DIMM_B1
DIMM_A2
DIMM_B2 DIMM_A1
128 Pins
112 Pins
Channel Socket
Channel A DIMM_A1 and DIMM_A2
Channel B DIMM_B1 and DIMM_B2
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