Fan 5 running at higher speed after updating IMM to version 1.33 - IBM System x

Resolving The Problem

Source

RETAIN tip: H21663

Symptom

After updating Integrated Management Module (IMM) firmware to version 1.33 Build ID: YUOOE3C or later, Fan 5 of IBM x3550 M3 systems with one (1) Central Processing Unit (CPU) and one (1) Power Supply Unit (PSU) installed will run at a higher speed.

Affected configurations

The system may be any of the following IBM servers:

• System x3550 M3, type 4254, any model
• System x3550 M3, type 7944, any model

This tip is not software specific.

This tip is not option specific.

The system has the symptom described above.

The following system firmware level(s) are affected:

• IMM version 1.33 (Build ID: YUOOE3C) or later
  

Workaround

This is working as design, there is no workaround.

Additional information

Prior to IMM version 1.33, an issue was discovered that in a specific configuration when one (1) CPU and one (1) PSU is installed in IBM System x3550 M3 while the ambient temperature is between 20 and 22 degrees Celsius (68 - 71.6 degrees Fahrenheit), the fan speed of the power supply is low and will result in a poor thermal condition for the BBU.

IMM version 1.33 or later has a modified fan speed table to improve the Intelligent Battery Backup Unit (iBBU) thermal condition. The issue described is a result of this modification.