HP Integrity rx8640, HP 9000 rp8440 Server User Service Guide

Thermal Monitoring
The manageability firmware is responsible for monitoring the ambient temperature in the server
and taking appropriate action if this temperature becomes too high. To this end, the ambient
temperature of the server is broken into four ranges: normal, overtemp low (OTL), overtemp medium
(OTM), and overtemp high (OTH). Figure 59 shows the actions taken at each range transition.
Actions for increasing temperatures are shown on the left; actions for decreasing temps are shown
on the right.
Figure 59 Temperature States
OTH
Normal
OTL
OTM
Send Chassis Code
Send Chassis Code
Send Chassis Code
Send Chassis Code
Send Chassis Code
Fan Speed = HIGH
Fan Speed = NORMAL
Send signal to the OS
Shut Down 48v
Reset
Send signal to the OS
On large temperature swings, the server will transition through all states in order. It may go to the
following state immediately, but each of the preceding actions will occur. If the temperature reaches
the highest range, the server will be shut down immediately by the manageability firmware.
Fan Control
There are three sets of fans in the system: those on the I/O bay, the front and rear fans that are
connected to the main backplane, and those on the cell boards. The front fans are run off of standby
power, and will be running any time AC input power is supplied to the server. All of the fans turn
on when 48 V power is supplied to the system.
As shown Figure 59, the fan behavior is related to the temperature state. The fans will be set to
high speed when the ambient temperature is anywhere above the normal operating range. The
front and rear fans will be set to high speed any time a chassis intrusion switch is triggered when
removing a side cover.
Altimeter Circuit
The PCI-X backplane contains an altimeter circuit. This circuit is used to adjust the chassis fan speeds
for the operating altitude at power on and during MP initialization. The chassis fans consist of the
nine front fans, the twelve rear fans, and the six PCI-X I/O assembly fans. If an altimeter failure is
detected, the information is logged as an Event ID then propagated to the OS level to be picked
up by monitoring diagnostics.
The altimeter circuit is checked at power on by the MP. If an expected value is returned from the
altimeter circuit, the altimeter is determined good. The altimeter reading is then set in non-volatile
random access memory (NVRAM) on board the core I/O card. If the value is ever lost like for a
core I/O replacement, the NVRAM will be updated at next boot provided the altimeter is functioning
normally. If the altimeter has failed, and the stable storage value has been lost because of a core
I/O failure or replacement, the MP will adjust the fan speeds for sea level operation.
NOTE: Fans driven to a high RPM in dense air cannot maintain expected RPM and will be
considered bad by the MP leading to a “False Fan Failure” condition.
124 Server Troubleshooting