Intel Xeon User Manual

Intel
®
82870P2 (P64H2)
116 Design Guide
M66EN Isolation Switch Solution
One possible solution is to place a single 5 kΩ ± 5% pull-up on the P64H2 side of the isolation
logic and a 5
kΩ ± 5% pull-up on the slot side after the isolation logic, but with its own isolation
switch, which uses an inverted version of the bus enable control signal. This way, when the
isolation logic has the bus disconnected, the slot side will be pulled up with a 5
kΩ ± 5% resistor.
When the isolation logic has the bus connected, the slot side resistor will be isolated, and the
M66EN line will be pulled up by the 5
kΩ ± 5% pull-up on the P64H2 side of the isolation logic.
Using this method, the P64H2 would only be sinking through a single 5
kΩ resistor at any time and
would always be meeting the PCI Local Bus Specification, Revision 2.2 on the M66EN pull-up
(PCI Local Bus Specification, Revision 2.2, Section 7.7.7). See Figure 8-17.
Figure 8-17. M66EN Isolation Switch Solution
PCI SLOT
M66EN
+3.3 V
+3.3 V
5 k
Ω
5 kΩ
PCI Bus
Isolation Switch
M66EN
Isolation
Switch
HxM66EN
PxM66EN
Intel
®
P64H2
HxBUSEN#

Intel Xeon Specifications

General

Brand	Intel
Model	Xeon
Category	Processor
Language	English