General Topology And Layout Guidelines; Figure 24. Topology For 370-Pin Socket Designs With Single-Ended Termination (Set); Table 10. Trace Guidelines For Figure 24; Table 11. Trace Width: Space Guidelines - Intel 815EG Design Manual

System Bus Design Guidelines
5.2

General Topology and Layout Guidelines

Figure 24. Topology for 370-Pin Socket Designs with Single-Ended Termination (SET)

Table 10. Trace Guidelines for Figure 24

Description
GMCH to PGA370
socket trace
NOTES:
1.
2.
3.
Table 11 contains the trace width: space ratios assumed for this topology. Three types of crosstalk
are considered in this guideline: Intragroup AGTL/AGTL+, Intergroup AGTL/AGTL+, and
AGTL/AGTL+ to non-AGTL/AGTL+. Intragroup AGTL/AGTL+ crosstalk involves interference
between AGTL/AGTL+ signals within the same group. Intergroup AGTL/AGTL+ crosstalk
involves interference from AGTL/AGTL+ signals in a particular group to AGTL/AGTL+ signals
in a different group. An example of AGTL/AGTL+ to non-AGTL/AGTL+ crosstalk is when
CMOS and AGTL/AGTL+ signals interfere with each other. The AGTL/AGTL+ signals consist of
the following groups: data signals, control signals, clock signals, and address signals.

Table 11. Trace Width: Space Guidelines

Intragroup AGTL/AGTL+ signals (same group AGTL/AGTL+)
Intergroup AGTL/AGTL+ signals (different group AGTL/AGTL+)
AGTL/AGTL+ to System Memory Signals
AGTL/AGTL+ to non-AGTL/AGTL+
NOTES:
1.
2.
52
GM CH
Z = 60 Ω ± 15%
0
Min. Length
(inches)
1.90
All AGTL/AGTL+ bus signals should be referenced to the ground plane for the entire route.
Use an intragroup AGTL/AGTL+ spacing : line width : dielectric thickness ratio of at least 2:1:1 for
microstrip geometry. If ε
= 4.5, this should limit coupling to 3.4%. For example, intragroup AGTL+
r
routing could use 10 mil spacing, 5 mil traces, and a 5 mil prepreg between the signal layer and the
plane it references (assuming a 4-layer motherboard design).
The recommended trace width is 5 mils, but not greater than 6 mils.
Crosstalk Type
Edge-to-edge spacing.
Units are in mils.
Max. Length Notes
(inches)
4.50 1, 2, 3
Trace Width:Space Ratios
®
Intel 815EG Chipset Platform Design Guide
PGA370
Socket
sys_bus_topo_PGA370
1, 2
5:10 or 6:12
5:15 or 6:18
5:30 or 6:36
5:25 or 6:24
R