Hub Interface
90
Design Guide
Using the recommended stackup, the Hub Interface 1.5 data signal traces must be routed 5 mils
wide. There must be 15 mils spacing between traces (5/15). To break out of the MCH and ICH3-S
packages, the Hub Interface data signals can be routed 5/5. The signals must be separated to 5/15
within 0.3 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 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 HISWING, and is sampled
by the ICH3-S using HITERM. (see
). Both HISWNG and HITERM can be generated
locally with a single voltage divider circuit as shown in
Table 7-6. Hub Interface 1.5 Signal Groups
Group
Signals
MCH
Intel
®
ICH3-S
Common Clock Signals
HI_A[11:8]
HI[11:8]
Source Synchronous Signals
HI_A[7:0], HI_STBF, HI_STBS
HI[7:0], HI_STBF, HI_STBS
Miscellaneous Signals
HIRCOMP_A, HISWNG_A, HIVREF_A
HICOMP, HITERM, HIREF
Table 7-7. Hub Interface 1.5 Routing Parameters
System Type
Trace Length
Min-Max
Trace Z
0
Trace
Width/Spacing
Breakout
Width/Spacing
266 MHz
3” – 20”
50
Ω
± 10%
5/15 mils
5/5 mils
(max dist = 0.3”)
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
)
0.35 ± 5%
For 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%
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 ...