Intel® 820E Chipset

R

Design Guide 171

For line section D (DRCG to last RIMM), the CTM/CTM# must be length-matched within ±2 mils. (Exact matching is recommended.) For section C, ±2 mil trace length matching is required for the CFM/CFM# signals.

Note: The total trace length matching for the entire CTM/CTM# signal trace (sections A+B+D) and for the

CFM/CFM# signal trace (sections A+B) is ±2 mils. (Exact length matching is recommended.)

Figure 91. Differential Clock Routing Diagram (Sections A, C & D)

Ground CLOCK CLOCK# Ground
Ground/Power Plane
22 mils 22 mils14 mils 14 mils
6 mils 6 mils6 mils
4.5 mils 4.5 mils
2.1 mils
1.4 mils
diff_clk_routing

Figure 92. Non-Differential Clock Routing Diagram (Section B)

Ground CLOCK/CLOCK# Ground
Ground/Power Plane
10 mils 10 mils18 mils
6 mils 6 mils
4.5 mils 4.5 mils
2.1 mils
1.4 mils
non-diff_clk_routing
The CFM/CFM# differential pair signals require termination using either 27 Ω, 1% or 28 Ω, 2% resistors and a 0.1 µF capacitor, as shown in the following figure.

Figure 93. Termination for Direct RDRAM* Clocking Signals CFM/CFM#

rambus_clk_term
R1
CFM
CFM#
R2
28
2%
or
27
1%
C1
0 .1 µF
28
2%
or
27
1%