Intel EP80579 Guide

Intel
®
EP80579 Integrated Processor Product Line—High-Speed Design Concerns
Intel
®
EP80579 Integrated Processor Product Line
Platform Design Guide May 2010
56 Order Number: 320068-005US
Equation 3. Total Flight Time
5.6.3 Bus Length Tuning Methodology
Many buses, such as memory and bus, require length tuning a group of signals. A
common way to do this is by routing the bus first to determine what the approximate
length range is, then picking an arbitrary signal. Sometimes this signal may be the
most difficult one to route or adjust to tune. Using the PCB trace length for this signal,
the solution space of remainder signals and strobes in the group can be determined.
Intel is able to provide a length tuning calculator spreadsheet. The calculator uses all
the specific routing parameters specified in previous section (minimum and maximum
lengths, tolerances, signal groups, and so on) to determine the solution space for the
bus in question.
5.7 System Bus Tuning
Routing PCB system buses (for example, DDR2 memory bus) requires length matching
within source synchronous groups. As a result, propagation-based length matching is
used to account for the strobe-to-signal skew effects. Propagation-based length
matching is described in the next section, followed by a routing example.
5.7.1 Compensating for Package Trace Length Differences
The first factor in length matching involves compensating for package trace length
differences for signals within the same strobe group. The package trace length is
defined as the trace segment between the die pad and component package pin. The
package lengths on the processor and the EP80579 introduce skew between different
signals as illustrated in the example given in Figure 31.
Note: Component A in Figure 31 represents a memory or I/O controller hub. This example
uses a strobe and data signal, which happen to have the shortest and longest package
trace lengths respectively.
velocity
component
length
component
velocityPCB
lengthPCB
velocity
length
timeflight
_
2
_
2
_
__
_
=
++
component1
component1_
Figure 31. Package Trace Length Differences
Longest Package Trace Length
Die Pad
Die Pad
Component A
Strobe Signal
Data Signal
Delta
Component Pin
PLC
Delta
Shortest Package Trace Length

Intel EP80579 Specifications

General

Brand	Intel
Model	EP80579
Category	Computer Hardware
Language	English