In Windows NT 4.0, multi-processor support required that the Stepping levels on your processors be matched.

Windows 2000 will run with mismatched Stepping levels, though you may experience erratic behavior.

If Windows 2000 detects mismatched CPU Stepping, you receive a System Event log entry similar to:

                                 -------------------------------------------------------------------------                                 Event ID Count Component    Message sample                                                                -------------------------------------------------------------------------                                 I   41    32   Application  The CPUs in this multiprocessor system are                                                   Popup        not all the same revision level.  To use all                                                              processors the operating system restricts                                                                 itself to the features of the least capable                                                               processor in the system.  Should problems                                                                 occur with this system, contact the CPU                                                                   manufacturer to see if this mix of processors                                                             is supported.