Intel EP80579 Guide

Intel
®
EP80579 Integrated Processor Product Line May 2010
Order Number: 320068-005US 57
High-Speed Design Concerns—Intel
®
EP80579 Integrated Processor Product Line
Each of the signals will have varying amounts of package skew. The amount of skew for
a particular signal is based on the difference between that signal’s package trace length
and the longest signal’s package trace length in the same signal group. For example,
signals with shorter package length will have more package trace length compensation
than signals with package lengths closer to the longest package trace.
To compensate for package-induced skew, all source synchronous motherboard trace
lengths are adjusted by the exact amount of package length compensation (PLC).
Equation 4 defines PLC for a particular signal. SignalX is any signal in the group that
does not have the longest package length. This includes the strobe signals.
Equation 4. Package Length Compensation (PLC) Definition
The signals with a package length less than the longest package trace in that group will
require additional motherboard trace length equal to SignalX
PLC
. Equation 4 yields a
zero PLC for the signal with the longest package length, so the signal with the longest
package length would require no amount of additional motherboard trace length.
Figure 32 illustrates PLC using a data signal as the longest package trace and strobe
signal as SignalX.
5.8 Common Layout Pit-Falls
This section describes common high speed issues found when laying out a PCB.
Examples will be provided to aid the board developer in avoiding these issues. The
signals described in this section pertain to high speed signals, such as those found on
the system bus, memory bus, etc.
5.8.1 Signal Parallelism
To minimize high-speed signal induced noise or cross-talk, limit or do not route signals
on adjacent layers parallel to each other. Figure 33 shows the proper and improper
methods for routing signals on adjacent layers.
SignalX
PLC
Maximum_Signal_In_Group
PackageLength
SignalX
PackageLength
–=
Figure 32. Example of PLC Compensation on the Motherboard
Longest Package Trace
Shortest Package Trace
Die Pad
Die Pad
Component Pin
PLC
Shortest Motherboard Trace
Component A
Routes to
Component B
Strobe Signal
Data Signal
Shortest Motherboard T race
Delta
Delta

Intel EP80579 Specifications

General

Brand	Intel
Model	EP80579
Category	Computer Hardware
Language	English