General Topology And Layout Guidelines; Figure 19. Topology For 370-Pin Socket Designs With Single-Ended Termination (Set); Table 9. Trace Guidelines For Figure 19; Table 10. Trace Width:space Guidelines - Intel 815 Design Manual

System Bus Design Guidelines
5.2

General Topology and Layout Guidelines

Figure 19. Topology for 370-Pin Socket Designs with Single-Ended Termination (SET)

Table 9. Trace Guidelines for Figure 19

GMCH to PGA370 socket trace
NOTES:
1. All AGTL/AGTL+ bus signals should be referenced to the ground plane for the entire route.
2. Use an intragroup AGTL/AGTL+ spacing : line width : dielectric thickness ratio of at least 2:1:1 for
microstrip geometry. If
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).
3. The recommended trace width is 5 mils, but not greater than 6 mils.
Table 10 contains the trace width space ratios assumed for this topology. Three types of cross-talk
are considered in this guideline: Intragroup AGTL/AGTL+, Intergroup AGTL/AGTL+, and
AGTL/AGTL+ to non-AGTL/AGTL+. Intragroup AGTL/AGTL+ cross-talk involves interference
between AGTL/AGTL+ signals within the same group. Intergroup AGTL/AGTL+ cross-talk
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+ cross-talk 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 10. 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. Edge-to-edge spacing.
2. Units are in mils.
46
G MCH
L(1): Z = 60 ± 15%
0
1, 2, 3
Description
= 4.5, this should limit coupling to 3.4%. For example, intragroup AGTL+
r
Cross-Talk Type
Min. Length (inches)
1.90
®
Intel 815 Chipset Platform Design Guide
PGA370 socket
sys_bus_topo_PGA370
Max. Length (inches)
4.50
1, 2
Trace Width:Space Ratios
5:10 or 6:12
5:15 or 6:18
5:30 or 6:36
5:25 or 6:24
R