Perfmon: Processor Spikes on Multiprocessor Computer

• Microsoft Windows NT Workstation versions 3.51 and 4.0
• Microsoft Windows NT Server versions 3.51 and 4.0

SYMPTOMS

On a multiprocessor computer, you may see periods where the processor usage percentage will spike to 100 percent and back to 0 percent. This spike may happen for an unspecified period of time and then it may return to normal. This spike will happen on all processors in the computer at the same time.

CAUSE

When Window NT queries a server for performance data, it uses a software timer that is shared among all the processors. On certain multiprocessor computers, this might report a time that is not properly synchronized with another processor. Therefore, the time counter occasionally becomes out of synch, causing the perfmon data to oscillate between a large positive and large negative number. This problem has only been seen, so far, on computers that are based on the Intel Multiprocessor Architecture.

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

MORE INFORMATION

For the fix to work correctly, it must be able to determine that it should use the 8254 chip to use as its base timer. On newer BIOS, there will be a table entry that the HAL will look at while initializing. On computers without a newer BIOS, you will have to add a /USE8254 to the appropriate line in the Boot.ini file.