Intel 925 - Pentium D 925 3.0GHz 800MHz 4MB-Cache Socket 775 CPU

R
Intel
®
82925X/82925XE MCH Datasheet 3
Contents
1 Introduction .......................................................................................................................13
1.1 Terminology..........................................................................................................15
1.2 Reference Documents..........................................................................................16
1.3 MCH Overview .....................................................................................................16
1.3.1 Host Interface........................................................................................16
1.3.2 System Memory Interface.....................................................................17
1.3.3 Direct Media Interface (DMI).................................................................18
1.3.4 PCI Express* Graphics Interface..........................................................18
1.3.5 System Interrupts..................................................................................19
1.3.6 MCH Clocking.......................................................................................20
1.3.7 Power Management..............................................................................20
2 Signal Description .............................................................................................................21
2.1 Host Interface Signals ..........................................................................................23
2.2 DDR2 DRAM Channel A Interface.......................................................................26
2.3 DDR2 DRAM Channel B Interface.......................................................................27
2.4 DDR2 DRAM Reference and Compensation.......................................................28
2.5 PCI Express* x16 Graphics Port Signals .............................................................28
2.6 Clocks, Reset, and Miscellaneous .......................................................................29
2.7 Direct Media Interface (DMI) ................................................................................29
2.8 Power and Ground ...............................................................................................30
2.9 Reset States and Pull-up/Pull-downs...................................................................30
3 Register Description..........................................................................................................35
3.1 Register Terminology ...........................................................................................35
3.2 Platform Configuration..........................................................................................37
3.3 General Routing Configuration Accesses............................................................38
3.3.1 Standard PCI Bus Configuration Mechanism.......................................38
3.3.2 Logical PCI Bus 0 Configuration Mechanism.......................................39
3.3.3 Primary PCI and Downstream Configuration Mechanism....................39
3.3.4 PCI Express* Enhanced Configuration Mechanism.............................40
3.3.5 Intel
®
82925X/925XE MCH Configuration Cycle Flowchart .................42
3.4 I/O Mapped Registers ..........................................................................................43
3.4.1 CONFIG_ADDRESS—Configuration Address Register ......................43
3.4.2 CONFIG_DATA—Configuration Data Register....................................44
4 Host Bridge/DRAM Controller Registers (D0:F0) .............................................................45
4.1 Device 0 Function 0 PCI Configuration Register Details .....................................48
4.1.1 VID—Vendor Identification (D0:F0)......................................................48
4.1.2 DID—Device Identification (D0:F0) ......................................................48
4.1.3 PCICMD—PCI Command (D0:F0).......................................................49
4.1.4 PCISTS—PCI Status (D0:F0)...............................................................50
4.1.5 RID—Revision Identification (D0:F0)....................................................51
4.1.6 CC—Class Code (D0:F0) .....................................................................51