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System Memory Design Guidelines (DDR-SDRAM)
7.3.6.10.
Command Topology 3 Length Matching Requirements
The routed length of the command signals, between the GMCH package ball and the SO-DIMM must be
within the range defined below, with respect to the associated clock reference length. Refer to Figure 55
for a definition of the various motherboard trace segments. The length of trace from the SO-DIMM to
the termination resistor need not be length matched. The length matching requirements are also depicted
in Figure 56. Refer to Section 7.1 for more details on length matching requirements.
Length range formula for SO-DIMM0:
= SCK/SCLK#[2:0] total reference length, including package length. See clock Section 7.3.1.
X
0
= CMD signal total length = GMCH package + L1, as shown in Figure 55,
Y
0
where: ( X
Length range formula for SO-DIMM1:
= SCK/SCLK#[5:3] total reference length, including package length. See clock Section 7.3.1.
X
2
= CMD signal total length = GMCH package length + L1 + L2 +L3, as shown in Figure 55,
Y
2
where: ( X
No length matching is required from SO-DIMM1 to the termination resistor. Figure 56 on the following
page depicts the length matching requirements between the command signals and clock. A nominal
CMD package length of 500 mils can be used to estimate baseline MB lengths. Refer to Section 7.2 for
more details on package length compensation.
118
– 1.0" ) ≤ Y
≤ ( X
+ 2.0" )
0
0
0
– 1.0" ) ≤ Y
≤ ( X
+ 2.0" )
1
1
1
®
Intel
852GM Chipset Platform Design Guide
R
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