Publication No. 500-657055-000 Rev. G
Handling and Installation 25
1.7 Installing PMCs
1.7.1 PMC Site (VIO)
VIO is the I/O voltage used for PCI bus termination. The PCI bus interface
requires strong parallel (pull-up) termination. Initially, the voltage for the pull-
ups was +5 V. Over time, with the need for power reduction and higher speeds,
+3.3 V devices became prevalent. +3.3 V devices can easily drive TTL signaling.
Higher speed PCI buses u3 V termination.
Figure 1-4 Keypin Installation and Setup
CAUTION
When Installing the keypins on the two PMC sites, the two keypins MUST be setup for the same voltage
level (Either in the 5 V position (installed) or in the 3.3 V (removed) position). This is due to the keypins
being on the same bus, if installed incorrectly this could cause damage.
J2
J3
J5
J1
KP6
KP5
Keypins (KP5 and KP6)
KP5
Installed = 5.0V
(Factory Default)
Field removable
for 3.3V
KP6
Installed = 5.0V
(Factory Default)
Field removable
for 3.3V
