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Direct Memory Access, Table 4-9., Default DMA Channel Assignments

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System Support 4.3.2 Direct Memory Access Direct Memory Access (DMA) is a method by which a device accesses system memory without involving the microprocessor. Although the DMA method has been traditionally used to transfer blocks of data to or from an ISA I/O device, PCI devices may also use DMA operation as well. The DMA method reduces the amount of CPU interactions with memory, freeing the CPU for other processing tasks. ✎ This section describes DMA in general. For detailed information regarding DMA operation, refer to the data manual for the Intel 82801 I/O Controller Hub. The 82801 ICH8 component includes the equivalent of two 8237 DMA controllers cascaded together to provide eight DMA channels, each (excepting channel 4) configurable to a specific device. Table 4-9 lists the default configuration of the DMA channels. Table 4-9. Default DMA Channel Assignments DMA Channel Device ID Controller 1 (byte transfers) 0 Spare 1 Audio subsystem 2 Diskette drive 3 Parallel port Controller 2 (word transfers) 4 Cascade for controller 1 5 Spare 6 Spare 7 Spare All channels in DMA controller 1 operate at a higher priority than those in controller 2. Note that channel 4 is not available for use other than its cascading function for controller 1. The DMA controller 2 can transfer words only on an even address boundary. The DMA controller and page register define a 24-bit address that allows data transfers within the address space of the CPU. In addition to device configuration, each channel can be configured (through PCI Configuration Registers) for one of two modes of operation: ■ LPC DMA ■ PC/PCI DMA The LPC DMA mode uses the LPC bus to communicate DMA channel control and is implemented for devices using DMA through the SCH5317 I/O controller such as the diskette drive controller. The PC/PCI DMA mode uses the REQ#/GNT# signals to communicate DMA channel control and is used by PCI expansion devices. The DMA logic is accessed through two types of I/O mapped registers; page registers and controller registers. 4-16 www.hp.com Technical Reference Guide

Section	Page
Title	1
Contents	3
Chap_1_Introduction_final_review.pdf	7
Introduction	7
1.1 About this Guide	7
1.1.1 Online Viewing	7
1.1.2 Hardcopy	7
1.2 Additional Information Sources	7
1.3 Model Numbering Convention	7
1.4 Serial Number	9
1.5 Notational Conventions	9
1.5.1 Values	9
1.5.2 Ranges	9
1.5.3 Register Notation and Usage	9
1.5.4 Bit Notation and Byte Values	9
1.6 Common Acronyms and Abbreviations	10
Chap_2_System_Overview_final.pdf	17
System Overview	17
2.1 Introduction	17
2.2 Features	18
2.3 Mechanical Design	20
2.3.1 Cabinet Layouts	21
2.3.2 Chassis Layouts	26
2.3.3 Board Layouts	30
2.4 System Architecture	33
2.4.1 Intel Processor Support	35
2.4.2 Chipset	36
2.4.3 Support Components	37
2.4.4 System Memory	37
2.4.5 Mass Storage	38
2.4.6 Serial and Parallel Interfaces	38
2.4.7 Universal Serial Bus Interface	38
2.4.8 Network Interface Controller	38
2.4.9 Graphics Subsystem	39
2.4.10 Audio Subsystem	39
2.5 Specifications	40
Chap_3_Processor_final_review.pdf	45
Processor/Memory Subsystem	45
3.1 Introduction	45
3.2 Intel Pentium Processors	46
3.2.1 Intel Processor Overview	46
3.2.2 Processor Upgrading	48
3.3 Memory Subsystem	48
Chap_4_System_Support_final_review.pdf	53
System Support	53
4.1 Introduction	53
4.2 PCI Bus Overview	53
4.2.1 PCI 2.3 Bus Operation	54
4.2.2 PCI Express Bus Operation	58
4.2.3 Option ROM Mapping	60
4.2.4 PCI Interrupts	60
4.2.5 PCI Power Management Support	60
4.2.6 PCI Connectors	61
4.3 System Resources	63
4.3.1 Interrupts	63
4.3.2 Direct Memory Access	68
4.4 Real-Time Clock and Configuration Memory	71
4.4.1 Clearing CMOS	71
4.4.2 Standard CMOS Locations	72
4.5 System Management	72
4.5.1 Security Functions	72
4.5.2 Power Management	74
4.5.3 System Status	75
4.5.4 Thermal Sensing and Cooling	75
4.6 Register Map and Miscellaneous Functions	76
4.6.1 System I/O Map	76
4.6.2 SCH5317 I/O Controller Functions	77
Chap_5_Input-Output_Interfaces_final_review.pdf	79
Input/Output Interfaces	79
5.1 Introduction	79
5.2 SATA Interfaces	79
5.2.1 SATA Programming	79
5.2.2 SATA Connector	81
5.2.3 RAID Functionality	81
5.3 Diskette Drive Interface	82
5.3.1 Diskette Drive Programming	82
5.3.2 Diskette Drive Connector	86
5.4 Serial Interface	87
5.4.1 Serial Connector	87
5.4.2 Serial Interface Programming	87
5.5 Parallel Interface	89
5.5.1 Standard Parallel Port Mode	89
5.5.2 Enhanced Parallel Port Mode	89
5.5.3 Extended Capabilities Port Mode	90
5.5.4 Parallel Interface Programming	90
5.5.5 Parallel Interface Connector	92
5.6 Keyboard/Pointing Device Interface	93
5.6.1 Keyboard Interface Operation	93
5.6.2 Pointing Device Interface Operation	95
5.6.3 Keyboard/Pointing Device Interface Programming	95
5.6.4 Keyboard/Pointing Device Interface Connector	99
5.7 Universal Serial Bus Interface	100
5.7.1 USB Data Formats	101
5.7.2 USB Programming	102
5.7.3 USB Connector	103
5.7.4 USB Cable Data	104
5.8 Audio Subsystem	105
5.8.1 HD Audio Controller	106
5.8.2 HD Audio Interface	106
5.8.3 HD Audio Codec	107
5.8.4 Audio Programming	108
5.8.5 Audio Specifications	110
5.9 Network Interface Controller	111
5.9.1 Wake-On-LAN Support	112
5.9.2 Alert Standard Format Support	112
5.9.3 Power Management Support	112
5.9.4 NIC Programming	113
5.9.5 NIC Connector	113
5.9.6 NIC Specifications	114
Chap_6_Integrated_Graphics_final_review.pdf	115
Integrated Graphics Subsystem	115
6.1 Introduction	115
6.2 Functional Description	116
6.3 Display Modes	118
6.4 Upgrading Graphics	119
6.5 VGA Monitor Connector	120
Chap_7_Power_and_Signal_final_review.pdf	121
Power and Signal Distribution	121
7.1 Introduction	121
7.2 Power Supply Assembly/Control	121
7.2.1 Power Supply Assembly	122
7.2.2 Power Control	124
7.2.3 Power Management	127
7.3 Power Distribution	128
7.4 Signal Distribution	131
Chap_8_BIOS_ROM_final_review.pdf	135
BIOS ROM	135
8.1 Introduction	135
8.2 ROM Flashing	136
8.2.1 Upgrading	136
8.2.2 Changeable Splash Screen	137
8.3 Boot Functions	137
8.3.1 Boot Device Order	137
8.3.2 Network Boot (F12) Support	138
8.3.3 Memory Detection and Configuration	138
8.3.4 Boot Error Codes	139
8.4 Setup Utility	140
8.5 Client Management Functions	149
8.5.1 System ID and ROM Type	150
8.5.2 Temperature Status	150
8.5.3 Drive Fault Prediction	150
8.6 SMBIOS	151
8.7 USB Legacy Support	151
App_A_Error_Messages__amp__Codes_final_review.pdf	153
A.1 Introduction	153
A.2 Beep/Power LED Codes	153
A.3 Power-On Self Test (POST) Messages	154
A.4 System Error Messages (1xx-xx)	157
A.5 Memory Error Messages (2xx-xx)	158
A.6 Keyboard Error Messages (30x-xx)	159
A.7 Printer Error Messages (4xx-xx)	160
A.8 Video (Graphics) Error Messages (5xx-xx)	160
A.9 Diskette Drive Error Messages (6xx-xx)	161
A.10 Serial Interface Error Messages (11xx-xx)	162
A.11 Modem Communications Error Messages (12xx-xx)	163
A.12 System Status Error Messages (16xx-xx)	164
A.13 Hard Drive Error Messages (17xx-xx)	165
A.14 Hard Drive Error Messages (19xx-xx)	167
A.15 Video (Graphics) Error Messages (24xx-xx)	168
A.16 Audio Error Messages (3206-xx)	168
A.17 DVD/CD-ROM Error Messages (33xx-xx)	169
A.18 Network Interface Error Messages (60xx-xx)	169
A.19 SCSI Interface Error Messages (65xx-xx, 66xx-xx, 67xx-xx)	170
A.20 Pointing Device Interface Error Messages (8601-xx)	171
App_B_ASCII_Character_Set_final_review.pdf	173
B.1 Introduction	173
App_C_Keyboard_final_review.pdf	177
C.1 Introduction	177
C.2 Keystroke Processing	177
C.2.1 PS/2-Type Keyboard Transmissions	179
C.2.2 USB-Type Keyboard Transmissions	180
C.2.3 Keyboard Layouts	180
C.2.4 Keys	183
C.2.5 Keyboard Commands	186
C.2.6 Scan Codes	187
C.3 Connectors	193

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Technical Reference Guide

System Support

4.3.2 Direct Memory Access

Direct Memory Access (DMA) is a method by which a device accesses system memory without

involving the microprocessor. Although the DMA method has been traditionally used to transfer

blocks of data to or from an ISA I/O device, PCI devices may also use DMA operation as well.

The DMA method reduces the amount of CPU interactions with memory, freeing the CPU for

other processing tasks.

✎

This section describes DMA in general. For detailed information regarding DMA operation, refer

to the data manual for the Intel 82801 I/O Controller Hub.

The 82801 ICH8 component includes the equivalent of two 8237 DMA controllers cascaded

together to provide eight DMA channels, each (excepting channel 4) configurable to a specific

device.

Table 4-9 lists the default configuration of the DMA channels.

All channels in DMA controller 1 operate at a higher priority

than those in

controller 2. Note

that channel 4 is not available for use other than its cascading function for controller 1. The DMA

controller 2 can transfer words only on an even address boundary. The DMA controller and page

that allows data transfers within the address space of the CPU.

In addition to device configuration, each channel can be configured (through PCI Configuration

Registers) for one of two modes of operation:

■

LPC DMA

■

PC/PCI DMA

The LPC DMA mode uses the LPC bus to communicate DMA channel control and is

implemented for devices using DMA through the SCH5317 I/O controller such as the diskette

drive controller.

The PC/PCI DMA mode uses the REQ#/GNT# signals to communicate DMA channel control

and is used by PCI expansion devices.

The DMA logic is accessed through two types of I/O mapped registers; page registers and

controller registers.

Table 4-9.

Default DMA Channel Assignments

DMA Channel

Device ID

Controller 1 (byte transfers)

Spare

Audio subsystem

Diskette drive

Parallel port

Controller 2 (word transfers)

Cascade for controller 1

Spare