Mobile Intel Pentium 4 Processor - M and Intel 845MP/MZ Chipset Platform Design Guide

Mobile Intel
®
Pentium
®
4 Processor-M and Intel
®
845MP/845MZ Chipset Platform
Design Guide 79
R
5.2.4.1. Clock Group Signal Length Matching Requirements
The MCH-M provides three differential clock pair signals for each SO-DIMM. A differential clock
pair is made up of a SCK signal and its complement signal SCK#. The differential pairs for one SO-
DIMM are:
SCK[0] / SCK#[0]
SCK[1] / SCK#[1]
SCK[2] / SCK#[2]
The differential pairs for the second SO-DIMM are:
SCK[3] / SCK#[3]
SCK[4] / SCK#[4]
SCK[5] / SCK#[5]
The SCK and SCK# lengths must include both the MCH-M Package Length plus the Motherboard Trace
Length.
Clock length matching is required between clock pairs to their specified SO-DIMM connector. The
differential clock pairs must be matched to ± 25 mils including MCH-M package lengths. Each SCK to
SCK# pair must be matched to ±10 mils including MCH-M package lengths.
Please note that the differential clocks must be 1.0 inch to 2.0 inches longer than the data and data strobe
signals, and 1.0 inch to 3.0 inches longer then the control and command signals. For information
covering the data and data strobe to clock length matching requirements reference 5.2.1.1, for
information covering the control signal to clock length matching requirements reference 5.2.2.1, and for
information covering the command signal to clock length matching requirements reference Section
5.2.3.1.2 and 5.2.3.2.2-update link. The diagrams below depict the clock length matching requirements.
Refer to the
Pentium
®
4 Processor-M in the 568 Pin Package and Intel
®
845MP/845MZ Chipset
Platform Trace Length Calculator
for package trace length data.