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Hub Interface
8.2.1.
Internal Layer Routing
Traces should be routed 4 mils wide with 8 mils trace spacing (4 on 8) and 20 mils spacing from other
signals. In order to break out of the Intel 855PM MCH and Intel 82801DBM ICH4-M packages, the
HI[7:0] signals can be routed 4 on 4. The signal must be separated to 4 on 8 within 300 mils from the
package.
The maximum HI[7:0] signal trace length is 6 inches. The HI[7:0] signals must be matched within ± 100
mils of the HI_STB differential pair. There is no explicit matching requirement between the individual
HI[7:0] signals.
The hub interface strobe signals should be routed as a differential pair, 4 mils wide with 8 mils trace
spacing (4 on 8). The maximum length for strobe signals is 6 inches. Each strobe signal must be the
same length and each HI[7:0] signal must be matched to within ± 100 mils of the strobe signals.
Table 45. Hub Interface Signals Internal Layer Routing Summary
Signal
HI_[7:0]
HI_STB
and
HI_STB#
8.2.2.
External Layer Routing
Traces should be routed 5 mils wide with 10 mils trace spacing (5 on 10) and 20 mils spacing from other
signals. In order to break out of the Intel 855PM MCH and Intel 82801DBM ICH4-M packages, the
HI[7:0] signals can be routed 5 on 5. The signals must be separated to 5 on 10 within 300 mils from the
package.
The hub interface strobe signals should be routed as a differential pair, 5 mils wide with 10 mils trace
spacing (5 on 10). The maximum length for the strobe signals is 6 inches. Each strobe signal must be the
same length, and each HI[7:0] signal must be matched to within ± 100 mils of the strobe signals.
178
Max
Width
Space
length
(mils)
(mils)
(inch)
6
4
8
6
4
8
Mismatch
Relative To
length
(mils)
± 100
Differential
HI_STB pair
±100
Data lines
®
Intel
855PM Chipset Platform Design Guide
R
Space with
Notes
other signals
(mils)
20
20
HI_STB and
HI_STB# must
be the same
length (± 10
mils)
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