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®
Intel
855GME Chipset and Intel
Hub Interface
8.1.2
8-Bit Hub Interface Signal Referencing
The 8-bit Hub Interface data signal traces (HI[11:0]) and the two Hub Interface strobe signals
(HI_STB/HI_STBS and HI_STB#/HI_STBF) must all be referenced to ground to insure proper
noise immunity.
8.1.3
8-Bit Hub Interface Strobe Signals
The Hub Interface strobe signals should be routed 5 mil width, 15 mil spacing. (See
strobe pair should have a minimum of 20 mils spacing from any adjacent signals.
Table 67.
Hub Interface 1.5 Strobe Signals Routing Summary
Strobe Signal
Requirements
5 mil width,
20 mil spacing
(from other
signals),
15 mil spacing
(intra-pair)
8.1.4
8-bit Hub Interface HIREF and HI_VSWING Generation/
Distribution
HIREF is the Hub Interface reference voltage. The 6300ESB uses HI_VSWING to control voltage
swing and impedance strength of the Hub Interface buffers. The HIREF and HI_VSWING voltage
requirement and associated resistor recommendations for the voltage divider circuit are listed in
Table
68. Four options are given for the divider circuit, choose the one that best supports your
platform.
Table 68.
8-Bit Hub Interface HIREF/HI_VSWING Generation Circuit Specifications
HIREF Voltage
Specification (V)
350 mV ± 2%
NOTES:Capacitance Values For All Options
7. C1 and C3 = 0.1 µF (near divider)
8. C2, C4, C5, C6 = 0.01 µF (near GMCHGMCH and 6300ESB)
9. The resistor values R1, R2, R3, R4, R5, R6, and R7 must be rated at 1% tolerance.
184
®
6300ESB ICH Embedded Platform Design Guide
Maximum Trace
Referencing
Length
8 inches
Ground
HI_VSWING Voltage
Specification (V)
800 mV ± 2%
Strobe Signal Length Matching
Each strobe signal must be the same length, and
each data signal must be matched within ± 0.25
inches of the strobe signal.
Recommended Values for the HIREF/
HI_VSWING Divider Circuit ( Ω )
Option A
(Figure
86&
Figure
R1 = 226 Ω ± 1%, R2 = 147 Ω ± 1%,
R3 = 113 Ω ± 1%
Option B
(Figure
86&
Figure
R1 = 80.6 Ω ± 1%, R2 = 51.1 Ω ± 1%,
R3 = 40.2 Ω ± 1%
Option C
(Figure
86&
Figure
R1 = 255 Ω ± 1%, R2 = 162 Ω ± 1%,
R3 = 127 Ω ± 1%
Option D
(Figure
88&
Figure
R4 = 78.7 Ω ± 1%, R5 = 24.2 Ω ± 1%,
R6 = 43.2 Ω ± 1%, R7 = 49.9 Ω ± 1%
Table
67.) This
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87)
87)
89)
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