Intel Xeon User Manual

Hub Interface
88 Design Guide
The resistor values R1, R2, R3, R4, R5, and R6 must be rated at ± 1% tolerance. The selected
resistor values must also ensure that the reference voltage and reference swing voltage tolerance
are maintained over the input leakage specification. A 0.1 µF capacitor (C1 in the above circuits)
should be placed close to each resistor divider, and a 0.01 µF bypass capacitor (C2 in the above
circuits) should be placed near each reference voltage pin. If the length of the trace from the
voltage divider to the pin is greater than 1", place more than one 0.01 µF capacitor near the
reference voltage pin. The trace length from the voltage divider circuit to the corresponding pin
must be no longer than 3.5 inches.
Both the voltage reference and voltage swing reference signals should be routed 20 mils to 25 mils
from all other signals.
7.2.3 Hub Interface 2.0 Resistive Compensation
The hub interface uses a resistive compensation signal (HIRCOMP_x) to compensate buffer
characteristics across temperature, voltage, and process. The HIRCOMP_x resistor values are
given in Table 7-5. Figure 7-6 shows the RCOMP_x circuits.
Figure 7-5. Hub Interface 2.0 with Locally Generated Voltage Divider Circuit
MCH
HISWNG_x
HIVREF_x
Intel
®
P64H2
0.35 V
0.35 V
0.8 V
0.8 V
HI_VSWING
HI_VREF
R4
R5
R6
R3
R2
R1
C2C1
C1
C1
C1
C2
C2
C2
1.2 V
1.8 V
Table 7-5. Hub Interface 2.0 RCOMP Resistor Values
Component Trace Impedance RCOMP Resistor Value RCOMP Resistor Tied To
MCH 50 Ω ± 10% R1 = 24.9 Ω ± 1% VCC1.2
Intel
®
P64H2 50 Ω ± 10% R2 = 61.9 Ω ± 1% VCC1.8
Figure 7-6. Hub Interface 2.0 RCOMP Circuits
MCH
HIRCOMP_x
R1
1.8 V
Intel
®
P64H2
HI_RCOMP
R2
1.2 V

Intel Xeon Specifications

General

Brand	Intel
Model	Xeon
Category	Processor
Language	English