panic: Wrong PMG (page map group): Explanation please

[Manavendra K. Thakur]

I need an explanation, please, of the following error message.

My machine (3/160, SunOS 4.1, 4MB, diskful) just died with the following
error:

	panic: wrong pmg
	syncing file systems... [15] 4 [15] 2 [13] [10] [5] done
	  .
	  . (Ususal messages about dumping pages)
	  .
	rebooting...

After the machine rebooted, I looked in the /var/adm/messages file and
found the following:

  vmunix: WRONG PAGE MAP GROUP FOUND FOR VIRTUAL ADDRESS 0x0fb80000!
  vmunix: PMG 0x0e0b6c20 claims VA 0x0f020000 is PMEG 0x000000ef (hardware)
  vmunix: PMG 0x0e0b6020 claims VA 0x0fb80000 is PMEG 0x0000006f (kernel)
  vmunix: PMG 0x0e0b6020 claims VA 0x0fb80000 is PMEG 0x0000006f (user)
  vmunix: panic: wrong pmg

and then the syncing file systems etc etc messages listed above.

Can anybody explain what these error messages mean?  Does this indicate a
hardware failure of any kind?  This is the first time my machine has
exhibited such an error (to the best of my knowledge), and I've been
running SunOS for since the beginning of May.

Please don't suggest that I provide a stack backtrace.  I can't provide
such a backtrace because I don't have the necessary vmcore files (the
machine rebooted spontaneously).

Any and all suggestions, hints, RTFMs, etc are welcomed.  I'm completely
in the dark as to what these messages might mean.

Manavendra K. Thakur
System Manager,				Internet: thakur at zerkalo.harvard.edu
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