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Intel® 41210 Serial to Parallel PCI Bridge Design Guide 37
PCI-X Layout Guidelines
Table 8. PCI-X Clock Layout Requirements Summary
Parameter Routing Guidelines
Signal Group PCI Clocks B_CLKO[6:0], A_CLK[6:0]
Reference Plane Route over unbroken ground or power plane
Stripline Trace Width 4 mils
Stripline Trace Spacing: Separation between two
different clock lines, “d” clock lines
25 mils center to center from any other signal
Stripline Trace Spacing: Separation between two
segments of the same clock line (on serpentine
layout), “a” dimension
25 mils center to center from any other signal
Stripline Trace Spacing: Separation between clocks
and other lines
50 mils center to center from any other signal
Length Matching Requirements
All 41210 Bridge Output Clocks B_CLK0[6:0] and
A_CLK[6:0] connected to devices must be length
matched to 0.1 inch of each other.
The clock feedback line lengths from A_CLKOUT to
A_CLKIN and B_CLKOUT to B_CLKIN should be
length matched to all other clock lines within 0.1”.
Total Length of the 41210 Bridge PCI CLKs on the
adapter card
10” -14”
A_CLKIN, B_CLKIN Series Termination
Connect A_CLKIN to one end of a 22Ω +/- 1% resistor
and the other end connected to A_CLKOUT and
connect B_CLKIN to one end of a 22Ω resistor and
the other end connected to B_CLKOUT
A_CLK[6:0], B_CLK[6:0] Series Termination
Each of the clock outputs A_CLKO[6:0] and
B_CLK[6:0] should have series 22Ω resistor located
within 500 mils of the 41210 Bridge clock output.
Routing Guideline 1
Point to point signal routing should be used to keep
the reflections low.
Routing Guideline 2 Minimize number of vias