Intel 820E manual Length Matching Methods, RSL Routing Layer Requirements

Intel® 820E Chipset

R

Figure 29. RSL Signal Layer Alternation

Signal on secondary side

Signal on primary side

Signal A

MCH

Signal B

Signal A

Route on EITHER layer.

Ground isolation is

REQUIRED!

		Term
	Signal B
		rsl_sig-lay_alter.vsd
Table 7. RSL Routing Layer Requirements
	MCH to 1st RIMM	1st RIMM to 2nd RIMM
Method 1	Primary side	Secondary side
Method 2	Secondary side	Primary side

2.7.2.6.Length Matching Methods

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 the RIMM connector, the length mismatch between the pad (on the die) and the ball has not been taken into account. However, given the package dimension, which represents 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 the matching of the trace lengths from pad to pin within ±10 mils.

Given the following definitions:

•Package dimension: Representation of length from pad to ball

•Board trace length: Trace length on board

•Nominal RSL length: 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 ±10 mils of the 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).

50 Design Guide