Intel D845PEMY User manual

August 2004
Order Number: C83645-001
The Intel®Desktop Board D845PEMY 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 D845PEMY Specification Update.
Intel®Desktop Board
D845PEMY
Technical Product Specification

Revision History
Revision Revision History Date
-001 First release of the Intel®Desktop Board D845PEMY Technical Product
Specification. August 2004
This product specification applies to only standard Intel®Desktop Board D845PEMY with BIOS
identifier FN84510A.86A.
Changes to this specification will be published in the Intel Desktop Board D845PEMY
Specification Update before being incorporated into a revision of this document.
INFORMATION IN THIS DOCUMENT IS PROVIDED IN CONNECTION WITH INTEL®PRODUCTS. EXCEPT AS
PROVIDED IN INTEL'S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, INTEL ASSUMES NO LIABILITY
WHATSOEVER, AND INTEL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY, RELATING TO SALE AND/OR USE
OF INTEL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR
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which the failure of the Intel product could create a situation where personal injury or death may occur.
Intel may make changes to specifications, product descriptions, and plans at any time, without notice.
The Intel®Desktop Board D845PEMY may contain design defects or errors known as errata that may cause the product to
deviate from published specifications. Current characterized errata are available on request.
Contact your local Intel sales office or your distributor to obtain the latest specifications before placing your product order.
Copies of documents which have an ordering number and are referenced in this document, or other Intel literature, may be
obtained from:
Intel Corporation
P.O. Box 5937
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countries.
*Other names and brands may be claimed as the property of others.
Copyright ©2004, 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 D845PEMY. It
describes the standard product and available manufacturing options.
Intended Audience
The TPS is intended to provide detailed, technical information about the Desktop Board
D845PEMY and their 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 D845PEMY
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 D845PEMY 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 D845PEMY, 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
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)
Mbit/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
1.2 Block Diagram..............................................................................................................13
1.3 Online Support.............................................................................................................14
1.4 Operating System Support...........................................................................................14
1.5 Processor.....................................................................................................................15
1.6 System Memory...........................................................................................................16
1.7 Intel®845PE Chipset ...................................................................................................18
1.7.1 AGP...............................................................................................................18
1.7.2 USB...............................................................................................................19
1.7.3 IDE Interfaces................................................................................................19
1.7.4 Real-Time Clock, CMOS SRAM, and Battery................................................20
1.8 I/O Controller................................................................................................................21
1.8.1 Serial Ports....................................................................................................21
1.8.2 Parallel Port...................................................................................................21
1.8.3 Diskette Drive Controller................................................................................21
1.8.4 Keyboard and Mouse Interface .....................................................................21
1.9 Audio Subsystem.........................................................................................................22
1.9.1 Front Panel Audio Connectors ......................................................................22
1.9.2 Audio Subsystem Software ...........................................................................22
1.10 LAN Subsystem ...........................................................................................................23
1.10.1 Intel®82562ET Platform LAN Connect Device..............................................23
1.10.2 RJ-45 LAN Connector with Integrated LEDs.................................................23
1.10.3 LAN Subsystem Software..............................................................................23
1.11 Hardware Management Subsystem (Optional)............................................................24
1.11.1 Hardware Monitoring and Fan Control ASIC.................................................24
1.11.2 Fan Monitoring...............................................................................................24
1.11.3 Chassis Intrusion and Detection....................................................................24
1.12 Power Management.....................................................................................................25
1.12.1 ACPI..............................................................................................................25
1.12.2 Hardware Support .........................................................................................27
2Technical Reference
2.1 Introduction ..................................................................................................................31
2.2 Memory Map................................................................................................................31
2.3 Fixed I/O Map...............................................................................................................32
2.4 DMA Channels.............................................................................................................33
2.5 PCI Configuration Space Map......................................................................................33
2.6 Interrupts......................................................................................................................34
2.7 PCI Interrupt Routing Map ...........................................................................................35

Intel Desktop Board D845PEMY Technical Product Specification
vi
2.8 Connectors...................................................................................................................37
2.8.1 Back Panel Connectors.................................................................................38
2.8.2 Internal I/O Connectors .................................................................................39
2.8.3 External I/O Connectors................................................................................44
2.9 Jumper Blocks..............................................................................................................48
2.9.1 Front Panel Audio Connector/Jumper Block .................................................48
2.9.2 BIOS Setup Configuration Jumper Block ......................................................49
2.10 Mechanical Considerations..........................................................................................50
2.10.1 I/O Shield.......................................................................................................51
2.11 Electrical Considerations..............................................................................................52
2.11.1 DC Loading....................................................................................................52
2.11.2 Add-in Board Considerations.........................................................................52
2.11.3 Fan Connector Current Capability.................................................................52
2.11.4 Power Supply Considerations .......................................................................53
2.12 Thermal Considerations...............................................................................................53
2.13 Reliability......................................................................................................................55
2.14 Environmental..............................................................................................................55
2.15 Regulatory Compliance................................................................................................56
2.15.1 Safety Regulations ........................................................................................56
2.15.2 EMC Regulations...........................................................................................56
2.15.3 European Union Declaration of Conformity Statement..................................57
2.15.4 Product Ecology Statements.........................................................................58
2.15.5 Product Certification Markings (Board Level)................................................58
3Overview of BIOS Features
3.1 Introduction ..................................................................................................................59
3.2 BIOS Flash Memory Organization ...............................................................................60
3.3 Resource Configuration ...............................................................................................60
3.3.1 PCI Autoconfiguration....................................................................................60
3.3.2 PCI IDE Support............................................................................................60
3.4 System Management BIOS (SMBIOS) ........................................................................61
3.5 Legacy USB Support....................................................................................................61
3.6 BIOS Updates..............................................................................................................62
3.6.1 Language Support.........................................................................................62
3.6.2 Custom Splash Screen..................................................................................62
3.7 Boot Options ................................................................................................................63
3.7.1 CD-ROM Boot ...............................................................................................63
3.7.2 Network Boot.................................................................................................63
3.7.3 Booting Without Attached Devices................................................................63
3.7.4 Changing the Default Boot Device During POST..........................................63
3.8 Fast Booting Systems with Intel®Rapid BIOS Boot.....................................................64
3.8.1 Peripheral Selection and Configuration.........................................................64
3.8.2 Intel Rapid BIOS Boot ...................................................................................64
3.9 BIOS Security Features ...............................................................................................65

Contents
vii
4Error Messages and Beep Codes
4.1 BIOS Error Messages..................................................................................................67
4.2 Port 80h POST Codes .................................................................................................69
4.3 Bus Initialization Checkpoints ......................................................................................73
4.4 Speaker .......................................................................................................................74
4.5 BIOS Beep Codes........................................................................................................74
Figures
1. Desktop Board D845PEMY Components....................................................................12
2. Block Diagram..............................................................................................................13
3. Location of the Standby Power Indicator LED on the D845PEMY Board....................30
4. Back Panel Connectors................................................................................................38
5. Audio, Power, and Hardware Control Connectors.......................................................40
6. Add-in Board and Peripheral Interface Connectors .....................................................43
7. External I/O Connectors...............................................................................................44
8. Connection Diagram for Front Panel Connector..........................................................45
9. Connection Diagram for Front Panel USB Connector..................................................47
10. Location of the Jumper Blocks.....................................................................................48
11. Desktop Board Dimensions..........................................................................................50
12. I/O Shield Dimensions..................................................................................................51
13. Localized High Temperature Zones.............................................................................54
Tables
1. Feature Summary ........................................................................................................10
2. Manufacturing Options.................................................................................................11
3. Supported System Bus Frequency and Memory Speed Combinations.......................16
4. Supported DDR DIMM Configurations.........................................................................17
5. LAN Connector LED States .........................................................................................23
6. Effects of Pressing the Power Switch ..........................................................................25
7. Power States and Targeted System Power.................................................................26
8. Wake-up Devices and Events......................................................................................27
9. Fan Connector Function/Operation..............................................................................28
10. System Memory Map ...................................................................................................31
11. I/O Map ........................................................................................................................32
12. DMA Channels.............................................................................................................33
13. PCI Configuration Space Map......................................................................................33
14. Interrupts......................................................................................................................34
15. PCI Interrupt Routing Map ...........................................................................................36
16. Front Panel Audio Connector.......................................................................................41
17. ATX12V Power Connector...........................................................................................41
18. Rear Chassis Fan Connector.......................................................................................41
19. Processor Fan Connector............................................................................................41
20. Main Power Connector.................................................................................................42
21. Front Chassis Fan Connector......................................................................................42
22. Chassis Intrusion Connector........................................................................................42
23. Serial Port B Connector (optional) ...............................................................................44
24. Auxiliary Front Panel Power/Sleep LED Connector.....................................................45
25. Front Panel Connector.................................................................................................45

Intel Desktop Board D845PEMY Technical Product Specification
viii
26. States for a One-Color Power LED..............................................................................46
27. States for a Two-Color Power LED..............................................................................46
28. Front Panel Audio Connector/Jumper Block................................................................49
29. BIOS Setup Configuration Jumper Settings.................................................................49
30. DC Loading Characteristics .........................................................................................52
31. Fan Connector Current Capability................................................................................52
32. Thermal Considerations for Components ....................................................................54
33. Desktop Board D845PEMY Environmental Specifications ..........................................55
34. Safety Regulations.......................................................................................................56
35. EMC Regulations.........................................................................................................56
36. Product Certification Markings.....................................................................................58
37. BIOS Setup Program Menu Bar...................................................................................60
38. BIOS Setup Program Function Keys............................................................................60
39. Boot Device Menu Options ..........................................................................................63
40. Supervisor and User Password Functions...................................................................65
41. BIOS Error Messages..................................................................................................67
42. Uncompressed INIT Code Checkpoints.......................................................................69
43. Boot Block Recovery Code Checkpoints .....................................................................69
44. Runtime Code Uncompressed in F000 Shadow RAM.................................................70
45. Bus Initialization Checkpoints ......................................................................................73
46. Upper Nibble High Byte Functions...............................................................................73
47. Lower Nibble High Byte Functions...............................................................................74
48. Beep Codes .................................................................................................................75

9
1 Product Description
What This Chapter Contains
1.1 Overview......................................................................................................................10
1.2 Block Diagram..............................................................................................................13
1.3 Online Support.............................................................................................................14
1.4 Operating System Support...........................................................................................14
1.5 Processor.....................................................................................................................15
1.6 System Memory...........................................................................................................16
1.7 Intel®845PE Chipset ...................................................................................................18
1.8 I/O Controller................................................................................................................21
1.9 Audio Subsystem.........................................................................................................22
1.10 LAN Subsystem ...........................................................................................................23
1.11 Hardware Management Subsystem (Optional)............................................................24
1.12 Power Management.....................................................................................................25

Intel Desktop Board D845PEMY Technical Product Specification
10
1.1 Overview
1.1.1 Feature Summary
Table 1 summarizes the major features of the Intel®Desktop Board D845PEMY.
Table 1. Feature Summary
Form Factor microATX (9.20 inches by 8.20 inches [233.68 millimeters by 208.28 millimeters])
Processor • Support for an Intel®Pentium®4 processor in an mPGA478 socket with a
400/533 MHz system bus
• Support for an Intel®Celeron®processor in an mPGA478 socket with a
400 MHz system bus
• Support for an Intel®Celeron®D processor in an mPGA478 socket with a
400 MHz system bus
Memory • Two 184-pin DDR SDRAM Dual Inline Memory Module (DIMM) sockets
• Support for single-sided or double-sided DIMMs (DDR333/266/200)
• Support for up to 2 GB of single-channel DDR memory
Chipset Intel®845PE Chipset, consisting of:
• Intel®82845PE Memory Controller Hub (MCH)
• Intel®82801DB I/O Controller Hub (ICH4)
• 3 Mbit Firmware Hub (FWH)
Video AGP connector supporting 1.5 V 4X AGP cards
Audio Audio subsystem for AC ‘97 processing using the Realtek ALC202A codec
I/O Control National Semiconductor PC87372 LPC Bus I/O controller (or equivalent)
LAN Intel®82562ET 10/100 Mbit/sec Platform LAN Connect (PLC) device
USB Support for USB 2.0 devices
Peripheral
Interfaces
• Up to four USB ports
• One serial port
• One parallel port
• Two IDE interfaces with UDMA 33, ATA-66/100 support
• One diskette drive interface
• PS/2* keyboard and mouse ports
• Three fan connectors
Expansion
Capabilities Three PCI bus add-in card connectors (SMBus routed to PCI bus connector 2)
BIOS • Intel/AMI BIOS (resident in the 3 Mbit FWH)
• Support for Advanced Configuration and Power Interface (ACPI), Plug and Play,
and SMBIOS
Instantly Available
PC Technology
• Support for PCI Local Bus Specification Revision 2.2
• Suspend to RAM support
• Wake on PCI, RS-232, front panel, PS/2 devices, and USB ports

Product Description
11
1.1.2 Manufacturing Options
Table 2 describes the manufacturing options on the Desktop Board D845PEMY. 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
Hardware Monitor
Subsystem
• Hardware monitoring and fan control ASIC
• Three fan sense inputs used to monitor fan activity
• Chassis intrusion detection
Serial Port B Connector for a second serial port
For information about Refer to
Available configurations for the Desktop Board D845PEMY Section 1.3, page 14

Intel Desktop Board D845PEMY Technical Product Specification
12
1.1.3 Board Layout
Figure 1 shows the location of the major components on the Desktop Board D845PEMY.
OM17286
C
A
E
G
I
H
F
D
SKMLOPQRNT
V
W
X
Y
Z
U
AA
B
J
Item Description Item Description
A Audio codec O Speaker
B Intel 82562ET 10/100 Mbit/sec (PLC) device P Battery
C Back panel connectors Q Auxiliary front panel power LED connector
D +12V power connector (ATX12V) R Front chassis fan connector
E Rear chassis fan connector S Chassis intrusion connector
F Intel 82845PE MCH T BIOS Setup configuration jumper block
G mPGA478 processor socket U 3 Mbit Firmware Hub (FWH)
H Processor fan connector V Front panel connector
I DIMM sockets W Front panel USB connector
J Serial Port B connector (optional) X Intel 82801DB I/O Controller Hub (ICH4)
K I/O Controller Y AGP connector
L Power connector Z PCI bus add-in card connectors
M Diskette drive connector AA Front panel audio connector
N IDE connectors
Figure 1. Desktop Board D845PEMY Components

Product Description
13
1.2 Block Diagram
Figure 2 is a block diagram of the major functional areas of the board.
Intel 845PE Chipset
Intel 82801DB
I/O Controller Hub
(ICH4)
Intel 82845PE
Memory Controller
Hub (MCH)
3 Mbit
Firmware Hub
(FWH)
AHA
Bus
System Bus
(400/533 MHz)
mPGA478
Processor Socket
Primary/
Secondary IDE
Diskette Drive
Connector
LPC Bus
I/O
Controller PS/2 Keyboard
PS/2 Mouse
Parallel Port
Serial Ports
UDMA 33 and
ATA-66/100
LPC
Bus
OM17295
Realtek
ALC202A
Audio Codec Mic In
Line Out
Line In
LAN
Connector
Physical
Layer
Interface
DIMM Banks (2)
= connector or socket
PCI Bus
SMBus
AC Link
Back Panel /
Front Panel
USB Ports
USB
4X AGP Connector
(1.5 V only)
AGP
Interface
Memory Bus
PCI Slot 1
PCI Slot 2
PCI Slot 3
SMBus
SMBus
CSMA/CD
Unit
Interface
Figure 2. Block Diagram

Intel Desktop Board D845PEMY Technical Product Specification
14
1.3 Online Support
To find information about… Visit this World Wide Web site:
Intel Desktop Board D845PEMY 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 D845PEMY http://developer.intel.com/design/motherbd/my/my_available.htm
Processor data sheets http://www.intel.com/design/litcentr
ICH4 addressing http://developer.intel.com/design/chipsets/datashts
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
1.4 Operating System Support
The Desktop Board D845PEMY supports drivers for all of the onboard hardware and subsystems
under the following operating systems:
• Windows* XP
• Windows ME
• Windows 2000
• Microsoft Windows 98 SE
For information about Refer to
Supported drivers Section 1.3

NOTE
Third party vendors may offer other drivers.

Product Description
15
1.5 Processor
The board is designed to support the following:
• Intel Pentium4 processors in an mPGA478 processor socket with a 533/400 MHz system bus
• Intel Celeron processors in an mPGA478 processor socket with a 400 MHz system bus
• Intel Celeron D processors in an mPGA478 processor socket with a 400 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 D845PEMY board http://www.intel.com/design/motherbd/my/my_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 NOTES
• Use only ATX12V-, SFX12V-, or TFX12V-compliant power supplies with the Desktop Board
D845PEMY. ATX12V, SFX12V, and TFX12V power supplies have an additional power lead
that provides required supplemental power for the processor. Always connect the 20-pin and
4-pin leads of ATX12V, SFX12V, and TFX12V power supplies to the corresponding connectors
on the desktop board, otherwise the board will not boot.
• Do not use a standard ATX power supply. The board will not boot with a standard ATX power
supply.
• Refer to Table 3 on page 16 for a list of supported system bus frequency and memory speed
combinations.
For information about Refer to
Power supply connectors Section 2.8.2.2, page 40

Intel Desktop Board D845PEMY Technical Product Specification
16
1.6 System Memory
The Desktop Board D845PEMY has two DIMM sockets and is designed to support up to 2 GB of
single-channel DDR SDRAM memory. The board supports the following memory features:
• 2.5 V (only) 184-pin DDR SDRAM DIMMs with gold-plated contacts
• Unbuffered single-sided or double-sided DIMMs
• Maximum total system memory: 2 GB; minimum total system memory: 64 MB
• DDR333/266/200 MHz SDRAM DIMMs only
• Serial Presence Detect (SPD)
• Suspend to RAM
Table 3 lists the supported system bus frequency and memory speed combinations.
Table 3. Supported System Bus Frequency and Memory Speed Combinations
If the processor's system bus frequency is… You can use this type of DIMM…
533 MHz DDR333 or DDR266
400 MHz DDR266 or DDR200
CAUTION
Do not use ECC DIMMs with this board. Using ECC DIMMs could damage the board.
#
INTEGRATOR’S NOTES
• Registered DIMMs are not supported.
• Double-sided x16 DIMMs are not supported.
• If a full-length PCI add-in card is installed in PCI bus connector 1 (the PCI bus connector
closest to the processor), remove the add-in card before installing or upgrading memory to
avoid interference with the memory retention mechanism.
NOTE
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.

Product Description
17
Table 4 lists the supported DDR DIMM configurations.
Table 4. Supported DDR DIMM Configurations
DIMM
Capacity Configuration
(Note) DDR SDRAM
Density DDR SDRAM Organization Front-side/Back-side Number of DDR SDRAM Devices
64 MB SS 64 Mbit 8 M x 8/empty 8
64 MB SS 128 Mbit 8 M x 16/empty 4
128 MB DS 64 Mbit 8 M x 8/8 M x 8 16
128 MB SS 128 Mbit 16 M x 8/empty 8
128 MB SS 256 Mbit 16 M x 16/empty 4
256 MB DS 128 Mbit 16 M x 8/16 M x 8 16
256 MB SS 256 Mbit 32 M x 8/empty 8
256 MB SS 512 Mbit 32 M x 16/empty 4
512 MB DS 256 Mbit 32 M x 8/32 M x 8 16
512 MB SS 512 Mbit 64 M x 8/empty 8
1024 MB DS 512 Mbit 64 M x 8/64 M x 8 16
Note: In this column, “DS” refers to double-sided memory modules (containing DDR SDRAM devices on both sides)
and “SS” refers to single-sided memory modules (containing DDR SDRAM devices on only one side).

Intel Desktop Board D845PEMY Technical Product Specification
18
1.7 Intel®845PE Chipset
The Intel 845PE chipset consists of the following devices:
• Intel 82845PE Memory Controller Hub (MCH) with Accelerated Hub Architecture (AHA) bus
• Intel 82801DB I/O Controller Hub (ICH4) with AHA bus
• Firmware Hub (FWH)
The MCH is a centralized controller for the system bus, the memory bus, the AGP bus, and the
Accelerated Hub Architecture interface. The ICH4 is a centralized controller for the board’s I/O
paths. The FWH provides the nonvolatile storage of the BIOS.
For information about Refer to
The Intel 845PE chipset http://developer.intel.com/
Resources used by the chipset Chapter 2
1.7.1 AGP
The AGP connector supports AGP add-in cards with 1.5 V Switching Voltage Level (SVL).
Legacy 3.3 V AGP cards are not supported.
For information about Refer to
The location of the AGP connector Figure 1, page 12
NOTE
Install memory in the DIMM sockets prior to installing the AGP video card to avoid interference
with the memory retention mechanism.

NOTE
The AGP connector is keyed for 1.5 V AGP cards only. Do not attempt to install a legacy 3.3 V
AGP card. The AGP connector is not mechanically compatible with legacy 3.3 V AGP cards.
AGP is a high-performance interface for graphics-intensive applications, such as 3D applications.
While based on the PCI Local Bus Specification, Rev. 2.2, AGP is independent of the PCI bus and
is intended for exclusive use with graphical display devices. AGP overcomes certain limitations of
the PCI bus related to handling large amounts of graphics data with the following features:
• Pipelined memory read and write operations that hide memory access latency
• Demultiplexing of address and data on the bus for nearly 100 percent efficiency

Product Description
19
1.7.2 USB
The board supports up to four USB 2.0 ports, fully supports UHCI and EHCI, and uses UHCI- and
EHCI-compatible drivers. For more than four USB devices, an external hub can be connected to
any of the ports.
The ICH4 provides the USB controller for all ports. The port arrangement is as follows:
• Two ports are implemented with stacked back panel connectors, adjacent to the audio
connectors
• Two ports are routed to the front panel USB connector

NOTE
Computer systems that have an unshielded cable attached to a USB port may not meet FCC
Class B requirements, even if no device is attached to the cable. Use shielded cable that meets the
requirements for full-speed devices.
1.7.3 IDE Interfaces
The ICH4’s IDE controller has two independent bus-mastering IDE interfaces that can be
independently enabled. The IDE interfaces support the following modes:
• Programmed I/O (PIO): processor controls data transfer.
• 8237-style DMA: DMA offloads the processor, supporting transfer rates of up to 16 MB/sec.
• Ultra DMA: DMA protocol on IDE bus supporting host and target throttling and transfer rates
of up to 33 MB/sec.
• ATA-66: DMA protocol on IDE bus supporting host and target throttling and transfer rates of
up to 66 MB/sec. ATA-66 protocol is similar to Ultra DMA and is device driver compatible.
• ATA-100: DMA protocol on IDE bus allows host and target throttling. The ICH4’s ATA-100
logic can achieve transfer rates up to 100 MB/sec.

Intel Desktop Board D845PEMY Technical Product Specification
20
#
INTEGRATOR’S NOTE
ATA-66 and ATA-100 are faster timings and require a specialized cable to reduce reflections,
noise, and inductive coupling.
The IDE interfaces also support ATAPI devices (such as CD-ROM drives) and ATA devices.
The BIOS supports 48-bit Logical Block Addressing (LBA) and Extended Cylinder Head Sector
(ECHS) translation modes. The drive reports the transfer rate and translation mode to the BIOS.
The Desktop Boards support Laser Servo (LS-120) diskette technology through the IDE interfaces.
The BIOS supports booting from an LS-120 drive.

NOTE
The BIOS will always recognize an LS-120 drive as an ATAPI floppy drive. To ensure correct
operation, do not configure the drive as a hard disk drive.
1.7.4 Real-Time Clock, CMOS SRAM, and Battery
A coin-cell battery (CR2032) powers the real-time clock and CMOS memory. When the computer
is not plugged into a wall socket, the battery has an estimated life of three years. When the
computer is plugged in, the standby current from the power supply extends the life of the battery.
The clock is accurate to ±13 minutes/year at 25 ºC with 3.3 VSB applied.
#
INTEGRATOR’S NOTE
If the battery and AC power fail, custom defaults, if previously saved, will be loaded into CMOS
RAM at power-on.