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Intel
®
855PM Chipset Platform Design Guide
5
5.7.
Voltage Regulator Topology ........................................................................................100
5.8.
Voltage Regulator Design Recommendations ............................................................100
5.8.1.
High Current Path, Top MOSFET Turned ON .............................................101
5.8.2.
High Current Paths During Abrupt Load Current Changes .........................101
5.8.3.
High Current Paths During Switching Dead Time........................................102
5.8.4.
High Current Path with Bottom MOSFET(s) Turned ON .............................102
5.8.5.
General Layout Recommendations .............................................................103
5.9.
Processor Decoupling Recommendations ..................................................................104
5.9.1.
Transient Response .....................................................................................104
5.9.2.
High Frequency, Mid Frequency, and Bulk Decoupling...............................105
5.9.3.
Processor Core Voltage Plane and Decoupling ..........................................106
5.9.4.
Intel Pentium M Processor / Intel Celeron M Processor
and Intel 855PM MCH V
CCP
Voltage Plane and Decoupling........................114
5.9.4.1.
Processor V
CCP
Voltage Plane and Decoupling............................114
5.9.4.2.
Intel 855PM MCH V
CCP
Voltage Plane and Decoupling................118
5.9.5.
Intel 855PM MCH Core Voltage Plane and Decoupling ..............................119
6.
System Memory Design Guidelines (DDR-SDRAM)................................................................125
6.1.
DDR 200/266/333 MHz System Memory Topology and Layout Design Guidelines ...126
6.1.1.
Data Signals – SDQ[71:0], SDQS[8:0].........................................................126
6.1.1.1.
Data to Strobe Length Matching Requirements............................129
6.1.1.2.
Strobe to Clock Length Matching Requirements ..........................131
6.1.1.3.
Data Routing Example ..................................................................133
6.1.1.4.
Support for Small Form Factor Design DDR Data Bus Routing ...134
6.1.2.
Control Signals – SCKE[3:0], SCS#[3:0] .....................................................134
6.1.2.1.
Control to Clock Length Matching Requirements .........................136
6.1.2.2.
Control Routing Example ..............................................................138
6.1.3.
Command Signals – SMA[12:0], SBS[1:0], SRAS#, SCAS#, SWE#...........139
6.1.3.1.
Command Topology 1 Solution.....................................................139
6.1.3.1.1.
Routing Description for Command Topology 1...........139
6.1.3.1.2.
Command Topology 1 to Clock Length Matching
Requirements..............................................................141
6.1.3.1.3.
Command Topology 1 Routing Example ....................143
6.1.3.2.
Command Topology 2 Solution.....................................................144
6.1.3.2.1.
Routing Description for Command Topology 2...........144
6.1.3.2.2.
Command Topology 2 to Clock Length Matching
Requirements..............................................................146
6.1.3.2.3.
Command Topology 2 Routing Example ....................148
6.1.4.
Clock Signals – SCK[5:0], SCK#[5:0] ..........................................................149
6.1.4.1.
Clock Signal Length Matching Requirements...............................151
6.1.4.1.1.
Clock Routing Example...............................................154
6.1.4.2.
Intel 855PM Chipset High Density Memory Support ....................155
6.1.5.
Feedback – RCVENOUT#, RCVENIN#.......................................................155
6.1.5.1.
RCVEN# Routing Example ...........................................................156
6.1.6.
Support for “DDP Stacked” SO-DIMM Modules ..........................................157
6.1.7.
Recommended Design Option to Support PC2700 DDR SDRAM
with Existing PC1600 and PC2100 Intel 855PM Platforms .........................158
6.1.7.1.
Shortened Data Signal Group Trace Length ................................158
6.1.7.1.1.
Supporting PC2700 Based on an Existing PC Platform
Layout .........................................................................158
6.1.7.1.2.
Additional Design Considerations for Adapting Intel
855PM DDR 200/266 MHz Platforms To Support
PC2700 .......................................................................159
6.2.
Intel 855PM MCH DDR Signal Package Lengths .......................................................160