Rsl Signal Layer Alternation; Rsl Routing Layer Requirements - Intel VC820 - Desktop Board Motherboard Design Manual

Figure 2-22. RSL Signal Layer Alternation
Table 2-4. RSL Routing Layer Requirements
Method 1
Method 2
2.6.2.6 Length Matching Methods
In order to allow for greater routing flexibility, the RSL signals require pad-to-pin length matching
between the MCH and the first connector. If the trace lengths are matched between the balls of the
MCH and the pin of RIMM connector, the length mismatch between the pad (on the die) and the
ball has not been accounted. However, given the package dimension, a representation of the length
from the pad to the ball, the routing can compensate for this package mismatch. Therefore, the
board length mismatch can be increased.
The RSL channel requires matching trace lengths from pad-to-pin within ±10 mils.
Given these definitions:
•
Package Dimension: a representation of the length from the pad to the ball.
•
Board Trace Length: the trace length on the board.
•
Nominal RSL Length: the length to which all signals are matched. (note: there is not
necessarily a trace that is EXACTLY to nominal length, but all RSL signals must be matched
to within ±10mil of a nominal length). The Nominal RSL Length is an arbitrary length (within
the limits of the routing guidelines) to which all the RSL signals will be matched (within
10 mils).
ALL RSL signals must meet the following equation.
®
Intel 820 Chipset Design Guide
Signal on Secondary Side
Signal on Primary Side
Signal A
MCH
Signal B
st st
MCH to 1 RIMM 1
Primary Side
Secondary Side
Layout/Routing Guidelines
Signal B
Signal A
Route on EITHER layer.
Ground Isolation is
REQUIRED!
nd
RIMM to 2 RIMM
Secondary Side
Primary Side
2-21