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

Intel
®
Xeon™ Processor and Intel
®
E7500/E7501 Chipset Compatible Platform Design Guide 141
Intel
®
82870P2 (P64H2)
M66EN Diode Solution
Another possible solution to the issue described in the previous paragraphs is to use diodes to
isolate the individual slots from one another while still allowing the P64H2 to drive the M66EN
signals to ground. The P64H2 PCI interface PxM66EN signal should be pulled to 3.3 V through a
100
kΩ ± 5% resistor. This signal would then be connected to the individual slots through a reverse
biased diode (one diode per slot). The PCI slots should also be pulled up individually to 3.3 V
through a resistor of value such that the equivalent of all the resistances on the M66EN bus is
approximately 5
kΩ (the PCI recommended value). This circuit allows the P64H2 to pull the slots’
M66EN to ground during initial power-up. During normal operation, each of the slots’ M66EN
signals will be isolated from one another allowing for polling of the Hot-Plug HxM66EN input for
slot capability. Figure 8-23 shows the diode solution implemented in serial mode, where “Slot x
M66EN” is a serialized input to the Hot-Plug controller.
.
NOTE: All PCI signals, multiplexed or not, must follow PCI Specification 2.2 pull-up requirements.
Figure 8-23. M66EN Diode Solution
Slot
4
Slot
3
Slot
2
Slot
1
20 kΩ
3.3 V
20 kΩ
3.3 V
20 kΩ
3.3 V
20 kΩ
3.3 V
100 kΩ
3.3V
M66EN M66EN M66ENM66EN
Slot 3 M66EN
Slot 4 M66EN
Slot 2 M66EN
Slot 1 M66EN
PxM66EN
PCI Interface
Hot Plug
Interface
Intel
®
P64H2