Design Guide
55
System Bus Routing Guidelines
Table 5-2. System Bus Routing Summary
Parameter
Platform Routing Guidelines
Trace Width/Spacing
5/15 mils.
2X and 4X Signal Group Line
Lengths
(Agent-to-Agent Length)
3.0" – 10.1" pin-to-pin.
Total bus length must not exceed 20.2".
Trace lengths must be balanced ± 25 mils with respect to the strobe between
agents to compensate for the stub created by the processor package.
DSTBN3[:0]# / DSTBP[3:0]#
and ADSTB[1:0]# Line
Lengths
Should follow the same routing rules as the 2X and 4X Signal Group.
A 25 mil spacing should be maintained around each strobe signal.
Do not route differentially.
Common Clock Signal Line
Lengths
Common Clock signals should follow the same routing rules as the Data
signals, however no length compensation is necessary.
Topology
Daisy chain with the chipset at one end of the system bus and Processor 0 at
the other.
End processor must have on-die termination enabled.
Routing Requirements
No motherboard contribution to stub length of middle processor (< 35 mil
trace from via to pad).
All signals within the same strobe group must be routed on same layer for
entire length of bus.
Reference Plane
Requirements
Ground referenced only.
Avoid changing layers when routing system bus signals.
If a layer change must occur, use vias connecting the two reference planes to
provide a low impedance path for the return current. Vias should be as close
as possible to the signal via.
For 2X and 4X signals, ADSTB[1:0]#, and DSTBN3[:0]# / DSTBP[3:0]#:
NEVER ROUTE OVER A PLANE SPLIT.
Motherboard Impedance
50
Ω ±
10%.
Summary of Contents for Xeon
Page 24: ...Introduction 24 Design Guide This page is intentionally left blank ...
Page 30: ...Component Quadrant Layout 30 Design Guide This page is intentionally left blank ...
Page 52: ...Platform Clock Routing Guidelines 52 Design Guide This page is intentionally left blank ...
Page 66: ...System Bus Routing Guidelines 66 Design Guide This page is intentionally left blank ...
Page 118: ...Intel 82870P2 P64H2 118 Design Guide This page is intentionally left blank ...
Page 146: ...I O Controller Hub 146 Design Guide This page is intentionally left blank ...
Page 148: ...Debug Port 148 Design Guide This page is intentionally left blank ...
Page 210: ...Schematic Checklist 210 Design Guide This page is intentionally left blank ...
Page 220: ...Layout Checklist 220 Design Guide This page is intentionally left blank ...
Page 222: ...Schematics 222 Design Guide This page is intentionally left blank ...