Hub Interface
R
Intel
®
855PM Chipset Platform Design Guide
179
Table 46. Hub Interface Signals External Layer Routing Summary
Signal Max
length
(inch)
Width
(mils)
Space
(mils)
Mismatch
length
(mils)
Relative To
Space with
other signals
(mils)
Notes
HI_[7:0] 6 5 10
±
100 Differential
HI_STB pair
20
HI_STB
and
HI_STB#
6
5
10
± 100
Data lines
20
HI_STB and
HI_STB# must
be the same
length (± 10
mils)
8.3.
Hub Interface Data HI[10:8] Signals
The maximum length for the hub interface data signals, HI[10:8] is 8 inches. They should be routed on
the same layer with Hl[7:0].
8.3.1.
Internal Layer Routing
Traces should be routed 4 mils wide with 8 mils trace spacing (4 on 8) and 20 mils spacing from other
non-hub interface related signals. In order to break out of the Intel 855PM MCH and Intel 82801DBM
ICH4-M packages, the HI[10:8] signals can be routed 4 on 4. The signal must be separated to 4 on 8
within 300 mils from the package.
8.3.2.
External Layer Routing
Traces should be routed 5 mils wide with 10 mils trace spacing (5 on 10) and 20 mils spacing from other
non-hub interface signals. In order to break out of the Intel 855PM MCH and Intel 82801DBM ICH4-M
packages, the HI[10:8] signals can be routed 5 on 5. The signal must be separated to 4 on 8 within 300
mils from the package.
8.3.3. Terminating
HI[11]
The HI[11] signal exists on the Intel 82801DBM ICH4-M but not the Intel 855PM MCH and is not used
on the platform. It can be left as a no connect.
8.4. HIREF/HI_VSWING
Generation/Distribution
HIREF is the hub interface reference voltage used on both the Intel 855PM MCH and the Intel
82801DBM ICH4-M. Depending on the buffer mode, the HIREF voltage requirement must be set
appropriately for proper operation. The ICH4-M uses HI_VSWING to control voltage swing and
impedance strength of the hub interface buffers. See the table below for the HIREF and HI_VSWING
voltage specifications and the associated resistor recommendations for the voltage divider circuit.
Содержание 855PM
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