Re: SUMMARY: ELC won't boot

From: Robert Terzi (rct@fid.Morgan.COM)
Date: Mon Dec 16 1991 - 14:36:58 CST

[ Sorry to continue Breaking The Rules, but the suggestion given for
  "fixing" NVRAM problems sounded way too dangerous to let pass... ]

Removing and/or replacing the NVRAM or *any* chip from a running machine
is a very bad idea, that at best, voids your warranty...

How to "Bail Out" Your Open Boot Prom 2.X

L1-F forces I/O to I/O to ttya, and stops the Open Boot Prom before it
        inteprets NVRAMRC. This leaves your NVRAM variables intact.
-- OR --

L1-N resets *ALL* NVRAM variables (including USE-NVRAMRC? and NVRAMRC
        to their defaults and then continues. You can then abort with L1-A
        to get back to the ok prompt, and use the nvrecover command to
        retrieve the contents of the NVRAMRC and fix them.
        (Or, of course you could just start over...)

In order for this to take affect, you must be hitting these keys at the
point in time, between after the machine has finished Power On Self Test
and before it attempts to execute NVRAMRC. (Hint: your probably
want to start hitting this sequence over and over when you are nearing
the end of POST.

This should be covered in the Open Boot Prom 2.X Documentation by


>> In "Re: SUMMARY: ELC won't boot", Dec 15, "(Alain Brossard EPFL-SI writes <<
> I do realize that I'm breaking the rules by replying directly,
> but it seems important enough since it may prevent managers from
> making their machines unusable at the hardware level.
> > From: (Stewart Castaldi)
> > (from monitor level)
> >
> > >n
> > ok nvedit
> (...)
> Some of you may be tempted to modify nvramrc using the
> eeprom command at the unix level. DO NOT DO THIS!!!! We tried
> it here and had to call sun to replace the NVRAM. I haven't had
> time to look at the source yet, but it seems that nvramrc is a
> (...)
> However if you screw up the NVRAM, here is a technique that should
> allow you to fix it at the risk of voiding your warranty and
> destroying another good NVRAM. Sun did it here and it worked so...
> Remove the NVRAM CAREFULLY, take care of the pins! Go to
> another similar machine (?), do a shutdown and bring it to monitor
> level (ok prompt). Open the case, remove CAREFULLY the good NVRAM,
> insert the new one CAREFULLY. During this time, the machine is still
> on line, so be carefull not to short anything. Now go back to the
> keyboard and fix the bad nvram. This may be as simple as setting
> use-nvramrc? to false, or you may use set-defaults to reset all
> the parameters to their default ones.
> Personnaly, I would rather call Sun and have them do
> it but then I hate hardware :-).

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