Intel BLKD955XCSLKR Configuration guide

July 2005
Order Number: D14066-001US
The Intel®Desktop Board D955XCS may contain design defects or errors known as errata that may cause the product to deviate from published specifications. Current
characterized errata are documented in the Intel Desktop Board D955XCS Specification Update.
Intel®Desktop Board
D955XCS
Technical Product Specification

Revision History
Revision Revision History Date
-001 First release of the Intel®Desktop Board D955XCS Technical Product
Specification July 2005
This product specification applies to only the standard Intel®Desktop Board D955XCS with BIOS
identifier BK95510J.86A.
Changes to this specification will be published in the Intel Desktop Board D955XCS Specification
Update before being incorporated into a revision of this document.
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Intel reserves these for future definition and shall have no responsibility whatsoever for conflicts or incompatibilities arising
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published specifications. Current characterized errata are available on request.
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Copyright ©2005, Intel Corporation. All rights reserved.

iii
Preface
This Technical Product Specification (TPS) specifies the board layout, components, connectors,
power and environmental requirements, and the BIOS for the Intel®Desktop Board D955XCS. It
describes the standard product and available manufacturing options.
Intended Audience
The TPS is intended to provide detailed, technical information about the Intel Desktop Board
D955XCS and its components to the vendors, system integrators, and other engineers and
technicians who need this level of information. It is specifically not intended for general audiences.
What This Document Contains
Chapter Description
1 A description of the hardware used on the Desktop Board D955XCS
2 A map of the resources of the Desktop Board
3 The features supported by the BIOS Setup program
4 A description of the BIOS error messages, beep codes, and POST codes
Typographical Conventions
This section contains information about the conventions used in this specification. Not all of these
symbols and abbreviations appear in all specifications of this type.
Notes, Cautions, and Warnings
 NOTE
Notes call attention to important information.
# INTEGRATOR’S NOTES
Integrator’s notes are used to call attention to information that may be useful to system integrators.
CAUTION
Cautions are included to help you avoid damaging hardware or losing data.
WARNING
Warnings indicate conditions, which if not observed, can cause personal injury.

Intel Desktop Board D955XCS Technical Product Specification
iv
Other Common Notation
# Used after a signal name to identify an active-low signal (such as USBP0#)
(NxnX) When used in the description of a component, N indicates component type, xn are the relative
coordinates of its location on the Desktop Board D955XCS, and X is the instance of the
particular part at that general location. For example, J5J1 is a connector, located at 5J. It is
the first connector in the 5J area.
GB Gigabyte (1,073,741,824 bytes)
GB/sec Gigabytes per second
Gbits/sec Gigabits per second
KB Kilobyte (1024 bytes)
Kbit Kilobit (1024 bits)
kbits/sec 1000 bits per second
MB Megabyte (1,048,576 bytes)
MB/sec Megabytes per second
Mbit Megabit (1,048,576 bits)
Mbits/sec Megabits per second
xxh An address or data value ending with a lowercase h indicates a hexadecimal value.
x.x V Volts. Voltages are DC unless otherwise specified.
* This symbol is used to indicate third-party brands and names that are the property of their
respective owners.

v
Contents
1Product Description
1.1 Overview......................................................................................................................10
1.1.1 Feature Summary..........................................................................................10
1.1.2 Manufacturing Options ..................................................................................11
1.1.3 Board Layout.................................................................................................12
1.1.4 Block Diagram...............................................................................................14
1.2 Online Support.............................................................................................................15
1.3 Processor.....................................................................................................................15
1.4 System Memory...........................................................................................................16
1.4.1 Memory Configurations .................................................................................17
1.5 Intel®955X Chipset......................................................................................................21
1.5.1 USB...............................................................................................................21
1.5.2 IDE Support...................................................................................................21
1.5.3 Real-Time Clock, CMOS SRAM, and Battery................................................23
1.6 Discrete Serial ATA Interface (Optional)......................................................................24
1.7 PCI Express* Connectors ............................................................................................24
1.8 Auxiliary Power (AUX PWR) Connector (Optional)......................................................25
1.9 IEEE-1394a/b Connectors (Optional)...........................................................................25
1.10 Legacy I/O Controller...................................................................................................26
1.10.1 Serial Port......................................................................................................26
1.10.2 Parallel Port...................................................................................................26
1.10.3 Diskette Drive Controller................................................................................26
1.10.4 Keyboard and Mouse Interface .....................................................................26
1.11 Audio Subsystem.........................................................................................................27
1.11.1 Audio Subsystem Software ...........................................................................27
1.11.2 Audio Connectors..........................................................................................27
1.11.3 8-Channel (7.1) Audio Subsystem.................................................................28
1.11.4 6-Channel (5.1) Audio Subsystem.................................................................30
1.12 LAN Subsystem ...........................................................................................................31
1.12.1 Intel®82573E/82573V Gigabit Ethernet Controller .......................................31
1.12.2 RJ-45 LAN Connector with Integrated LEDs.................................................31
1.12.3 Alert Standard Format (ASF) Support (Optional) ..........................................32
1.12.4 Intel®Active Management Technology (AMT) (Optional)..............................32
1.12.5 LAN Subsystem Software..............................................................................34
1.13 Hardware Management Subsystem.............................................................................34
1.13.1 Hardware Monitoring and Fan Control ASIC.................................................34
1.13.2 Thermal Monitoring........................................................................................35
1.13.3 Fan Monitoring...............................................................................................36
1.13.4 Chassis Intrusion and Detection....................................................................36
1.14 Power Management.....................................................................................................36
1.14.1 ACPI..............................................................................................................36
1.14.2 Hardware Support .........................................................................................39
1.15 Trusted Platform Module (Optional).............................................................................42

Intel Desktop Board D955XCS Technical Product Specification
vi
2Technical Reference
2.1 Memory Resources......................................................................................................43
2.1.1 Addressable Memory.....................................................................................43
2.1.2 Memory Map..................................................................................................45
2.2 DMA Channels.............................................................................................................45
2.3 Fixed I/O Map...............................................................................................................46
2.4 PCI Configuration Space Map......................................................................................47
2.5 Interrupts......................................................................................................................48
2.6 PCI Conventional Interrupt Routing Map .....................................................................49
2.7 Connectors...................................................................................................................51
2.7.1 Back Panel Connectors.................................................................................51
2.7.2 Component-side Connectors.........................................................................54
2.8 Jumper Block ...............................................................................................................65
2.9 Mechanical Considerations..........................................................................................66
2.9.1 Form Factor...................................................................................................66
2.9.2 I/O Shield.......................................................................................................67
2.10 Electrical Considerations..............................................................................................69
2.10.1 DC Loading....................................................................................................69
2.10.2 Add-in Board Considerations.........................................................................69
2.10.3 Fan Connector Current Capability.................................................................70
2.10.4 Power Supply Considerations .......................................................................70
2.11 Thermal Considerations...............................................................................................71
2.12 Reliability......................................................................................................................73
2.13 Environmental..............................................................................................................74
2.14 Regulatory Compliance................................................................................................75
2.14.1 Safety Regulations ........................................................................................75
2.14.2 EMC Regulations...........................................................................................75
2.14.3 European Union Declaration of Conformity Statement..................................76
2.14.4 Recycling Considerations..............................................................................77
2.14.5 Product Certification Markings (Board Level)................................................78
3Overview of BIOS Features
3.1 Introduction ..................................................................................................................79
3.2 Resource Configuration ...............................................................................................80
3.2.1 PCI Autoconfiguration....................................................................................80
3.2.2 PCI IDE Support............................................................................................80
3.3 System Management BIOS (SMBIOS) ........................................................................81
3.4 Legacy USB Support....................................................................................................81
3.5 BIOS Updates..............................................................................................................82
3.5.1 Language Support.........................................................................................82
3.5.2 Custom Splash Screen..................................................................................82
3.6 Boot Options ................................................................................................................83
3.6.1 CD-ROM Boot ...............................................................................................83
3.6.2 Network Boot.................................................................................................83
3.6.3 Booting Without Attached Devices................................................................83
3.6.4 Changing the Default Boot Device During POST..........................................83

Contents
vii
3.7 Fast Booting Systems with Intel®Rapid BIOS Boot.....................................................84
3.7.1 Peripheral Selection and Configuration.........................................................84
3.7.2 Intel Rapid BIOS Boot ...................................................................................84
3.8 BIOS Security Features ...............................................................................................85
4Error Messages and Beep Codes
4.1 Speaker .......................................................................................................................87
4.2 BIOS Beep Codes........................................................................................................87
4.3 BIOS Error Messages..................................................................................................87
4.4 Port 80h POST Codes .................................................................................................88
Figures
1. Desktop Board Components........................................................................................12
2. Block Diagram..............................................................................................................14
3. Memory Channel and DIMM Configuration..................................................................17
4. Dual Channel (Interleaved) Mode Configuration with Two DIMMs ..............................18
5. Dual Channel (Interleaved) Mode Configuration with Three DIMMs............................18
6. Dual Channel (Interleaved) Mode Configuration with Four DIMMs..............................19
7. Single Channel (Asymmetric) Mode Configuration with One DIMM.............................20
8. Single Channel (Asymmetric) Mode Configuration with Three DIMMs........................20
9. Front/Back Panel Audio Connector Options for 8-Channel (7.1) Audio Subsystem....28
10. 8-channel (7.1) Audio Subsystem Block Diagram........................................................29
11. Front/Back Panel Audio Connector Options for 6-Channel (5.1) Audio Subsystem....30
12. 6-Channel (5.1) Audio Subsystem Block Diagram.......................................................30
13. LAN Connector LED Locations....................................................................................31
14. Sensors and Fan Connectors ......................................................................................35
15. Location of the Standby Power Indicator LED .............................................................42
16. Detailed System Memory Address Map.......................................................................44
17. Back Panel Connectors for 8-Channel (7.1) Audio Subsystem ...................................52
18. Back Panel Connectors for 6-Channel (5.1) Audio Subsystem ...................................53
19. Component-side Connectors .......................................................................................54
20. Connection Diagram for Front Panel Connector..........................................................61
21. Connection Diagram for Front Panel USB Connectors................................................63
22. Connection Diagram for Front Panel IEEE 1394a/b Connectors.................................64
23. Location of the Jumper Block.......................................................................................65
24. Board Dimensions........................................................................................................66
25. I/O Shield Dimensions for Boards with the 8-Channel (7.1) Audio Subsystem............67
26. I/O Shield Dimensions for Boards with the 6-Channel (5.1) Audio Subsystem............68
27. Example of a Processor Heatsink for Omni-directional Airflow....................................71
28. Localized High Temperature Zones.............................................................................72
Tables
1. Feature Summary ........................................................................................................10
2. Manufacturing Options.................................................................................................11
3. Components Shown in Figure 1...................................................................................13
4. Supported Memory Configurations ..............................................................................16
5. LAN Connector LED States .........................................................................................31
6. Effects of Pressing the Power Switch ..........................................................................37

Intel Desktop Board D955XCS Technical Product Specification
viii
7. Power States and Targeted System Power.................................................................38
8. Wake-up Devices and Events......................................................................................39
9. System Memory Map ...................................................................................................45
10. DMA Channels.............................................................................................................45
11. I/O Map ........................................................................................................................46
12. PCI Configuration Space Map......................................................................................47
13. Interrupts......................................................................................................................48
14. PCI Interrupt Routing Map ...........................................................................................50
15. Back Panel Connectors Shown in Figure 17................................................................52
16. Back Panel Connectors Shown in Figure 18................................................................53
17. Component-side Connectors Shown in Figure 19 .......................................................55
18. ATAPI CD-ROM Connector (Optional).........................................................................56
19. Front Panel Audio Connector.......................................................................................56
20. Front Chassis Fan and Rear Chassis Fan Connectors...............................................56
21. Processor Fan Connector and Auxiliary Fan Connector..............................................56
22. Chassis Intrusion Connector........................................................................................57
23. Serial ATA Connectors.................................................................................................57
24. Auxiliary Power (AUX PWR) Output Connector (Optional)..........................................57
25. Main Power Connector.................................................................................................59
26. Processor Power Connector (2 x 4 Pin).......................................................................59
27. Processor Power Connector (2 x 2 Pin).......................................................................59
28. Auxiliary PCI Express Power Connector......................................................................59
29. Auxiliary Front Panel Power/Sleep LED Connector.....................................................60
30. Front Panel Connector.................................................................................................61
31. States for a One-Color Power LED..............................................................................62
32. States for a Two-Color Power LED..............................................................................62
33. BIOS Setup Configuration Jumper Settings.................................................................65
34. DC Loading Characteristics .........................................................................................69
35. Fan Connector Current Capability................................................................................70
36. Thermal Considerations for Components ....................................................................73
37. Environmental Specifications.......................................................................................74
38. Safety Regulations.......................................................................................................75
39. EMC Regulations.........................................................................................................75
40. Product Certification Markings.....................................................................................78
41. BIOS Setup Program Menu Bar...................................................................................80
42. BIOS Setup Program Function Keys............................................................................80
43. Boot Device Menu Options ..........................................................................................83
44. Supervisor and User Password Functions...................................................................85
45. Beep Codes .................................................................................................................87
46. BIOS Error Messages..................................................................................................87
47. Port 80h POST Code Ranges......................................................................................88
48. Port 80h POST Codes .................................................................................................89
49. Typical Port 80h POST Sequence...............................................................................92

9
1 Product Description
What This Chapter Contains
1.1 Overview......................................................................................................................10
1.2 Online Support.............................................................................................................15
1.3 Processor.....................................................................................................................15
1.4 System Memory...........................................................................................................16
1.5 Intel®955X Chipset......................................................................................................21
1.6 Discrete Serial ATA Interface (Optional)......................................................................24
1.7 PCI Express Connectors..............................................................................................24
1.8 Auxiliary Power (AUX PWR) Connector (Optional)......................................................25
1.9 IEEE-1394a/b Connectors (Optional)...........................................................................25
1.10 Legacy I/O Controller...................................................................................................26
1.11 Audio Subsystem.........................................................................................................27
1.12 LAN Subsystem ...........................................................................................................31
1.13 Hardware Management Subsystem.............................................................................34
1.14 Power Management.....................................................................................................36
1.15 Trusted Platform Module (Optional).............................................................................42

Intel Desktop Board D955XCS Technical Product Specification
10
1.1 Overview
1.1.1 Feature Summary
Table 1 summarizes the major features of the board.
Table 1. Feature Summary
Form Factor BTX (12.80 inches by 10.50 inches [325.12 millimeters by 266.71 millimeters])
Processor Support for an Intel®Pentium®4 processor in an LGA775 socket with a 1066 or
800 MHz system bus
Memory •Four 240-pin DDR2 SDRAM Dual Inline Memory Module (DIMM) sockets
•Support for 667 and 533 MHz DDR2 DIMMs
•Support for up to 8 GB of system memory
•Support for ECC and non-ECC memory
Chipset Intel®955X Chipset, consisting of:
•Intel®82955X Memory Controller Hub (MCH)
•Intel®82801GR I/O Controller Hub (ICH7-R)
Audio Intel®High Definition Audio subsystem
Legacy I/O Control Legacy I/O controller
USB Support for USB 2.0 devices
Peripheral
Interfaces
•Eight USB ports
•One serial port
•One parallel port
•Four Serial ATA interfaces with RAID support
•One Parallel ATA IDE interface with UDMA 33, ATA-66/100 support
•One diskette drive interface
•PS/2* keyboard and mouse ports
BIOS •Intel®BIOS (resident in the FWH or SPI Flash device)
•Support for Advanced Configuration and Power Interface (ACPI), Plug and Play,
SMBIOS, and Intel®Active Management Technology (Intel®AMT)
Instantly Available
PC Technology
•Support for PCI Local Bus Specification Revision 2.3
•Support for PCI Express* Revision 1.0a
•Suspend to RAM support
•Wake on PCI, RS-232, front panel, PS/2 devices, and USB ports
LAN Support Gigabit (10/100/1000 Mbits/sec) LAN subsystem using the Intel®82573E/82573V
Gigabit Ethernet Controller
Expansion
Capabilities
•Four PCI Conventional* bus add-in card connectors (SMBus routed to PCI
Conventional bus connector 2)
•One PCI Express x16 bus add-in card connector
•One Secondary PCI Express x16/x4 bus add-in card connector
•One PCI Express x1 bus add-in card connector
continued

Product Description
11
Table 1. Feature Summary (continued)
Hardware Monitor
Subsystem
•Hardware monitoring and fan control ASIC
•Voltage sense to detect out of range power supply voltages
•Thermal sense to detect out of range thermal values
•Three fan connectors
•Three fan sense inputs used to monitor fan activity
•Fan speed control
1.1.2 Manufacturing Options
Table 2 describes the manufacturing options. Not every manufacturing option is available in all
marketing channels. Please contact your Intel representative to determine which manufacturing
options are available to you.
Table 2. Manufacturing Options
ATAPI CD-ROM
connector A 1 x 4-pin ATAPI-style connector for connecting an internal ATAPI CD-ROM drive to
the audio mixer
Audio Subsystem Intel High Definition Audio subsystem in one of the following configurations:
•8-channel (7.1) audio subsystem with five analog audio outputs and two S/PDIF
digital audio outputs (coaxial and optical) using the Sigmatel* 9223 audio codec
•6-channel (5.1) audio subsystem with three analog audio outputs using the
Sigmatel 9220 audio codec
Auxiliary PCI
Express Power
Connector
Provides required additional power when using high power (75 W or greater) add-in
cards in both the PCI Express x16 and the Secondary PCI Express x16/x4 bus add-in
card connectors
Auxiliary Power
(AUX PWR)
Connector
Provides power for internal chassis lighting
Discrete SATA
RAID controller
•Silicon Image Sil 3114 SATA RAID controller
•Four SATA connectors (in addition to the four SATA connectors on the ICH7-R
SATA interface)
IEEE-1394a/b
Interface IEEE-1394a/b controller and three IEEE-1394a/b connectors: one back panel
connector, two front-panel connectors. Back panel connector is IEEE-1394a-
compatible only; front panel connectors are 1394a- or 1394b-compatible, configurable
through the BIOS Setup program.
Processor power
connector One of the following connectors for providing +12 V power to the processor voltage
regulator:
•2 x 4-pin (requires a power supply with a dual-rail 2 x 4 power cable)
•2 x 2-pin
Trusted Platform
Module (TPM) A component that enhances platform security
For information about Refer to
Available configurations for the board Section 1.2, page 15

Intel Desktop Board D955XCS Technical Product Specification
12
1.1.3 Board Layout
Figure 1 shows the location of the major components.
OM18043
BA I J KG H
R
O
M
N
L
P
JJ
LL
PP
NN
KK
OO
MM
II
HH GG DD BBFF EE U T
V
WXYZAA S
CC
D
E
F
Q
C
Figure 1. Desktop Board Components
Table 3 lists the components identified in Figure 1.

Product Description
13
Table 3. Components Shown in Figure 1
Item/callout from Figure 1 Description
A Front panel audio connector
B Back panel connectors
C Chassis intrusion connector
D Front panel USB connectors [2]
E Serial ATA connectors (ICH7-R RAID) [4]
F Power connector
G PCI Express x1 bus add-in card connector
H PCI Express x16 bus add-in card connector
I Legacy I/O controller
J PCI Conventional bus add-in card connector
K Secondary PCI Express x16/x4 bus add-in card connector
L PCI Conventional bus add-in card connectors [3]
M IEEE-1394a/b PHY component (optional)
N Auxiliary power connector (optional)
O IEEE-1394a/b Link component (optional)
P IEEE-1394a/b front panel connectors [2]
Q Auxiliary front panel power LED connector
R Serial ATA RAID controller (Discrete RAID) (optional)
S Serial ATA RAID connectors (Discrete RAID) (optional) [2]
T Auxiliary fan connector
U Serial ATA RAID connectors (Discrete RAID) (optional) [2]
V Front panel connector
W Front chassis fan connector
X Diskette drive connector
Y BIOS Setup configuration jumper block
Z Firmware Hub (FWH)
AA Auxiliary PCI Express power connector (optional)
BB Speaker
CC Intel 82801GR I/O Controller Hub (ICH7-R)
DD LGA775 processor socket
EE Intel 82955X MCH
FF Battery
GG Processor power connector
HH Processor fan connector
II DIMM Channel A sockets [2]
JJ DIMM Channel B sockets [2]
KK Rear chassis fan connector
LL SPI Flash device
MM Parallel ATA IDE connector
NN ATAPI CD-ROM connector (optional)
OO Audio codec
PP Gigabit Ethernet Controller

Intel Desktop Board D955XCS Technical Product Specification
14
1.1.4 Block Diagram
Figure 2 is a block diagram of the major functional areas of the board.
Intel 955X Chipset
Intel 82801GR
I/O Controller Hub
(ICH7-R)
Intel 82955X Memory
Controller Hub (MCH)
Firmware
Hub (FWH)
System Bus
(1066/800 MHz)
LGA775
Processor Socket
Parallel ATA
IDE Connector
Diskette Drive
Connector
LPC Bus
I/O
Controller PS/2 Keyboard
PS/2 Mouse
Parallel Port
Serial Port
Parallel ATA
IDE Interface
LPC Bus
Hardware Monitoring
and Fan Control ASIC
OM17986
Audio
Codec Line Out/Retasking Jack
CD-ROM (Optional)
PCI Express
x16 Interface
PCI Express
x16
Connector
PCI Bus
SMBus
High Definition Audio Link
USB
Dual-Channel
Memory Bus
SMBus
PCI Slot 1
PCI Slot 2
PCI Slot 3
Mic In/Retasking Jack
Line In/Retasking Jack
S/PDIF
SATA IDE
Connectors (4)
SATA IDE
Interface
Channel A
DIMMs (2)
Channel B
DIMMs (2)
Back Panel/Front Panel
USB Ports
Surround Left-Right/Retasking Jack
Center and LFE/Retasking Jack
Front Panel Mic In
Front Panel Line Out
DMI Interconnect
PCI
Bus
TPM Component
(Optional)
LPC Bus
PCI Express x1 Slot
Secondary PCI
Express x16/x4 Slot
LAN
Connector
Gigabit Ethernet
Controller
PCI Express Interface
SPI Flash
Device
-- or --
SMBus
SMBus
SATA RAID
Connectors (4)
(Optional)
PCI
Bus
Discrete SATA RAID
Controller
(Optional)
IEEE-1394a/b Connectors
(Optional)
IEEE-1394a/b
Controller
(Optional)
PCI Slot 4
Figure 2. Block Diagram

Product Description
15
1.2 Online Support
To find information about… Visit this World Wide Web site:
Intel®Desktop Board D955XCS under
“Desktop Board Products” or “Desktop
Board Support”
http://www.intel.com/design/motherbd
http://support.intel.com/support/motherboards/desktop
Available configurations for the Desktop
Board D955XCS http://developer.intel.com/design/motherbd/cs/cs_available.htm
Processor data sheets http://www.intel.com/design/litcentr
ICH7-R addressing http://developer.intel.com/products/chipsets
Custom splash screens http://intel.com/design/motherbd/gen_indx.htm
Audio software and utilities http://www.intel.com/design/motherbd
LAN software and drivers http://www.intel.com/design/motherbd
Intel®Active Management Technology http://www.intel.com/technology/manage/iamt/index.htm
1.3 Processor
The board is designed to support Intel Pentium4 processors in an LGA775 processor socket with a
1066 or 800 MHz system bus. See the Intel web site listed below for the most up-to-date list of
supported processors.
For information about… Refer to:
Supported processors for the board http://www.intel.com/design/motherbd/cs/cs_proc.htm
CAUTION
Use only the processors listed on web site above. Use of unsupported processors can damage the
board, the processor, and the power supply.
# INTEGRATOR’S NOTE
This board has specific requirements for providing power to the processor. Refer to Section 2.7.2.1
on page 58 for information on power supply requirements for this board.

Intel Desktop Board D955XCS Technical Product Specification
16
1.4 System Memory
The board has four DIMM sockets and supports the following memory features:
•1.8 V and 1.9 V DDR2 SDRAM DIMMs
•Unbuffered, single-sided or double-sided DIMMs with the following restriction:
Double-sided DIMMS with x16 organization are not supported.
•8 GB maximum total system memory. Refer to Section 2.1.1 on page 43 for information on the
total amount of addressable memory.
•Minimum total system memory: 128 MB
•ECC DIMMs and non-ECC DIMMs
•Serial Presence Detect
•DDR2 667 and 533 MHz SDRAM DIMMs
NOTES
To be fully compliant with all applicable DDR SDRAM memory specifications, the board should be
populated with DIMMs that support the Serial Presence Detect (SPD) data structure. This allows
the BIOS to read the SPD data and program the chipset to accurately configure memory settings
for optimum performance. If non-SPD memory is installed, the BIOS will attempt to correctly
configure the memory settings, but performance and reliability may be impacted or the DIMMs
may not function under the determined frequency.
Table 4 lists the supported DIMM configurations.
Table 4. Supported Memory Configurations
DIMM
Capacity Configuration
(Note 1) SDRAM
Density SDRAM Organization Front-side/Back-side Number of SDRAM Devices (Note 2)
128 MB SS 256 Mbit 16 M x 16/empty 4 [5]
256 MB SS 256 Mbit 32 M x 8/empty 8 [9]
256 MB SS 512 Mbit 32 M x 16/empty 4 [5]
512 MB DS 256 Mbit 32 M x 8/32 M x 8 16 [18]
512 MB SS 512 Mbit 64 M x 8/empty 8 [9]
512 MB SS 1 Gbit 64 M x 16/empty 4 [5]
1024 MB DS 512 Mbit 64 M x 8/64 M x 8 16 [18]
1024 MB SS 1 Gbit 128 M x 8/empty 8 [9]
2048 MB DS 1 Gbit 128 M x 8/128 M x 8 16 [18]
Notes:
1. In the second column, “DS” refers to double-sided memory modules (containing two rows of SDRAM) and “SS” refers to
single-sided memory modules (containing one row of SDRAM).
2. In the fifth column, the number in brackets specifies the number of SDRAM devices on an ECC DIMM.
# INTEGRATOR’S NOTE
Refer to Section 2.1.1, on page 43 for additional information on available memory.

Product Description
17
1.4.1 Memory Configurations
The Intel 82955X MCH supports two types of memory organization:
•Dual channel (Interleaved) mode. This mode offers the highest throughput for real world
applications. Dual channel mode is enabled when the installed memory capacities of both
DIMM channels are equal. Technology and device width can vary from one channel to the
other but the installed memory capacity for each channel must be equal. If different speed
DIMMs are used between channels, the slowest memory timing will be used.
•Single channel (Asymmetric) mode. This mode is equivalent to single channel bandwidth
operation for real world applications. This mode is used when only a single DIMM is installed
or the memory capacities are unequal. Technology and device width can vary from one
channel to the other. If different speed DIMMs are used between channels, the slowest
memory timing will be used.
Figure 3 illustrates the memory channel and DIMM configuration.
 NOTE
The DIMM0 sockets of both channels are blue. The DIMM1 sockets of both channels are black.
OM17987
Channel A, DIMM 0
Channel A, DIMM 1
Channel B, DIMM 0
Channel B, DIMM 1
Figure 3. Memory Channel and DIMM Configuration

Intel Desktop Board D955XCS Technical Product Specification
18
1.4.1.1 Dual Channel (Interleaved) Mode Configurations
Figure 4 shows a dual channel configuration using two DIMMs. In this example, the DIMM0
(blue) sockets of both channels are populated with identical DIMMs.
OM17988
Channel A, DIMM 0
Channel A, DIMM 1
Channel B, DIMM 0
Channel B, DIMM 1
1 GB
1 GB
Figure 4. Dual Channel (Interleaved) Mode Configuration with Two DIMMs
Figure 5 shows a dual channel configuration using three DIMMs. In this example, the combined
capacity of the two DIMMs in Channel A equal the capacity of the single DIMM in the DIMM0
(blue) socket of Channel B.
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Channel A, DIMM 0
Channel A, DIMM 1
Channel B, DIMM 0
Channel B, DIMM 1
256 MB
256 MB
512 MB
Figure 5. Dual Channel (Interleaved) Mode Configuration with Three DIMMs

Product Description
19
Figure 6 shows a dual channel configuration using four DIMMs. In this example, the combined
capacity of the two DIMMs in Channel A equal the combined capacity of the two DIMMs in
Channel B. Also, the DIMMs are matched between DIMM0 and DIMM1 of both channels.
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Channel A, DIMM 0
Channel A, DIMM 1
Channel B, DIMM 0
Channel B, DIMM 1
256 MB
512 MB
512 MB
256 MB
Figure 6. Dual Channel (Interleaved) Mode Configuration with Four DIMMs

Intel Desktop Board D955XCS Technical Product Specification
20
1.4.1.2 Single Channel (Asymmetric) Mode Configurations
 NOTE
Dual channel (Interleaved) mode configurations provide the highest memory throughput.
Figure 7 shows a single channel configuration using one DIMM. In this example, only the DIMM0
(blue) socket of Channel A is populated. Channel B is not populated.
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Channel A, DIMM 0
Channel A, DIMM 1
Channel B, DIMM 0
Channel B, DIMM 1
256 MB
Figure 7. Single Channel (Asymmetric) Mode Configuration with One DIMM
Figure 8 shows a single channel configuration using three DIMMs. In this example, the combined
capacity of the two DIMMs in Channel A does not equal the capacity of the single DIMM in the
DIMM0 (blue) socket of Channel B.
OM17992
Channel A, DIMM 0
Channel A, DIMM 1
Channel B, DIMM 0
Channel B, DIMM 1
256 MB
512 MB
512 MB
Figure 8. Single Channel (Asymmetric) Mode Configuration with Three DIMMs