Intel Xeon Processor and Intel E7500/E7501Chipset Compatible Platform Design Guide

Hub Interface
110 Intel
®
Xeon™ Processor and Intel
®
E7500/E7501 Chipset Compatible Platform Design Guide
Route the Hub Interface 1.5 data signal traces 5 mils wide using the recommended stack-up. There
must be 15 mils spacing between data signal traces (5/15). Each strobe signal must have a
minimum of 35 mils of spacing from any adjacent signals to minimize effects that cause signal
degradation. To break out of the MCH and ICH3-S package, the hub interface data signals can be
routed 5/5. The signals must separate to 5/15 (or strobes to 5/35) within 0.5 inch of the package.
For Hub Interface 1.5 devices on the motherboard, each strobe signal trace must be the same
length, and each data signal trace must be matched with respect to the strobes within ± 0.1 inch.
7.3.2 Hub Interface 1.5 Generation/Distribution of Reference
Voltages
The nominal Hub Interface 1.5 reference voltage is 0.35 V ± 5%. The 8-bit Hub Interface on the
MCH has a dedicated HIVREF pin to sample this reference voltage. In addition to the reference
voltage, a reference swing voltage must be supplied to control buffer voltage swing characteristics.
The nominal Hub Interface 1.5 reference voltage swing must be 0.8 V ±
5% for the MCH and
0.7 V ±
5% for the ICH3-S. This voltage is sampled by the MCH using HISWNG, and is sampled
by the ICH3-S using HITERM (see Table 7-8). Both HISWNG and HITERM can be generated
locally with a single voltage divider circuit as shown in Figure 7-8.
Table 7-8. Hub Interface 1.5 Reference Circuit Specifications
Reference Voltage
Specification (V)
Reference Swing Voltage
Specification (V)
1.2 V Voltage
Divider Circuit
Recommended
Resistor Values
(Ω)
1.8 V Voltage
Divider Circuit
Recommended
Resistor Values
(Ω)
Decoupling
Requirements
(µF)
0.35 ± 5%
For Intel
®
ICH3-S = 0.7 ± 5%
For MCH = 0.8 ± 5%
R1 = 392 ± 1%
R2 = 499 ± 1%
R3 = 453 ± 1%
R4 = 261 ± 1%
R5 = 825 ± 1%
C1 = 0.1
C2 = 0.01
Figure 7-8. Hub Interface 1.5 Locally Generated Reference Divider Circuits
HISWNG_A
HIVREF_A
Intel
®
ICH3-S
0.35 V
0.35 V
0.7 V
0.8 V
HITERM
HIREF
R4
R4
R5R3
R2
R1
C2C1
C1C1
C1
C2C2
C2
1.2 V
1.8 V
MCH