Product specifications

Design Guide - VT82C694X Apollo Pro133 with VT82C686A
Preliminary Revision 0.5, November 19, 1999 29 Motherboard Design Guidelines
Technologies, Inc.
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2.3 General Layout and Routing Guidelines
This section provides general layout rules and routing guidelines for designing Apollo Pro133A motherboards.
2.3.1 Trace Attribute Recommendations
For most signal traces on an Apollo Pro133A motherboard layout, 5-mil trace width and 10-mil spacing are advised. To reduce
trace inductance, minimum power trace width is set at 30 mils. As a quick reference, recommended trace width and spacing for
different trace types are listed in Table 2-6.
Table 2-6. Recommended Trace Width and Spacing
Trace Type Trace Width (mils) Spacing (mils)
Signal 5 or wider 10 or wider
Clock 15 or wider 15 or wider
Power 30 or wider 20 or wider
In high-speed bus design, general rules for minimizing crosswalk are listed below:
• Maximize the distance between traces. Maintain a minimum 10 mils space between traces wherever possible.
• Avoid parallelism between traces on adjacent layers.
• Select a board stack-up that minimizes coupling between adjacent traces.
• The recommended motherboard impedance should be in the range of 65 ohm +/- 5 ohm.