Intel 855Pm Mch Agtl+ I/O Buffer Compensation; Figure 35. Processor Comp[2] And Comp[0] 18-Mil Wide Dog Bones And Traces - Intel 855PM Design Manual

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Figure 35. Processor COMP[2] and COMP[0] 18-Mil Wide Dog Bones and Traces

PRIMARY SIDE PRIMARY SIDE
PRIMARY SIDE PRIMARY SIDE
COMP2 COMP2
4.1.8.2.

Intel 855PM MCH AGTL+ I/O Buffer Compensation

The Intel 855PM MCH AGTL+ I/O buffer resistive compensation signals pins of the MCH,
HRCOMP[1:0], should each be pulled-down to ground with a 27.4
length from pin to resistor should be less than 0.5 inches long and includes the dog bone connection on
the primary side from the BGA land to the dog bone via. This < 0.5 inch long connection should be 18
mils wide to achieve the Zo = 27.4
away from any switching signal. Figure 36 illustrates the recommended layout for the Intel 855PM
MCH HRCOMP[1:0] resistors that are placed on the motherboard's secondary side to save space as well
as to make the shortest possible connection without interacting with FSB routing. To avoid GND via
interaction of the HRCOMP[1:0] resistors, each should share the ground pin vias of the MCH's AE1
and AD12 ground pins to make the ground connection.
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Intel 855PM Chipset Platform Design Guide
COMP0 COMP0
COMP1 COMP1
18-mil Dog Bone 18-mil Dog Bone
COMP3 COMP3
target. Also, the routing for HRCOMP should be at least 25 mils
SECONDARY SIDE SECONDARY SIDE
27.4Ω 1% 27.4Ω 1%
SECONDARY SIDE SECONDARY SIDE
± 1% resistor. The maximum trace
FSB Design Guidelines
18-mil Trace 18-mil Trace
27.4Ω 1% 27.4Ω 1%
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