Diagnostics may incorrectly report CMOS checksum error - IBM eServer xSeries 450

Resolving The Problem

Source
RETAIN tip H181101

Symptoms

• The problem is that the diagnostics and SAL/EFI calculate the CMOS checksum differently.
• This problem has been seen when the CMOS diagnostic is executed after a system was reset or powered off during POST. If this happens, you will see this problem in the diagnostics when the CMOS test is run.
• If you power on a system and press the reset button when 23 is seen on the hex display and then run the CMOS diagnostic, you will see this problem.
• If you exit diagnostics, the system will reboot. If diagnostics is run again, the error will not reoccur.

Affected configurations

• The system may be any model of the IBM eServer xSeries 450 server, type 8688.
• The system is configured with MZYT12A diagnostics.
• The system's diagnostics fail.
• The BIOS level(s) affected is/are MZKT32A.

Solution
Download and apply the latest diagnostics (MZYT20A or later) which is available from System Firmware Update version 1.01

Workaround
Reset the system and rerun the diagnostics without interrupting POST.

Additional information
The problem is that the diagnostics and SAL/EFI calculate the CMOS checksum differently.
 
When POST is interrupted, a flag is set in CMOS which affects the checksum calculated by diagnostics and diagnostics reports this as an error.