> I've found that OS 8.6 is EXCEPTIONALLY sensitive to ram and disk
> directory integrity. I have a G3 tower with 512mb ram. Everything ran
> fine on 8.5.1 (which is quite fault tolerant) but I had repeated
> system bus errors after upgrading to 8.6. Careful checking narrowed
> this to a bad 64mb ram module (1 of 8) which ran faultless under
> 8.5.1. Each module was individually tested with TT2.1.1 and isolated
> bootup.
It's a bit facile to say "8.5.1 is fault tolerant and 8.6 is picky".
More likely a coincidence, in that something terribly important
happened to load into the bad RAM on your 8.6 install, while the
earlier install had (not exactly fortunately in that it masks a serious
problem) put something much less crucial there. This would likely be
particular to your machine model and extension set, since those affect
what gets loaded and when. My own policy is to test the hell out of
any new memory (including that in a new machine) as soon as I get it
(that also precludes turning off the POST RAM test right away, near-useless
though it is).
Your problem sounds like it was a badly corrupted power manager, though
it's always tough to say in retrospect. It's even possible that the
2400/3400 has a design flaw that allows the power management firmware
to get into a (soft!) state from which it sometimes can't extricate
itself - thus our dead motherboards aren't really dead, they just need
some extraordinary measure to reset them that we can't supply. But that
too is only a theory (not a particularly pretty one, since odds are
every 2400 would eventually reach that state, and no fix would be
permanent). And it doesn't particularly jibe with my experience, where
the problems seemed to be progressive, so take it very much with a grain
of salt.
> --Screen freezes while online (and probably offline) can severely
> corrupt PRAM and disk directories.
It's important to note that these two things aren't particularly
related. Directory corruption is pretty simple, and results entirely
from the OS being interrupted before it can write out some cached data
belonging to the directory. PRAM corruption is a bit more nebulous, and
power manager corruption more bizarre still.
> --The 2400 perhaps demands a cleaner disk directory than other PBs,
> irrespective of 603e or G3 CPU, but this may be specific to OS 8.6
> (remembering that a clean install of 8.6 is not possible for OS 8.5
> updaters and may have partial influence)
Sorry, but this is absurd. :) I think you may be reaching an
understandable but hasty conclusion from a single experience here, but
the bottom line is that this theory doesn't work. I'm not picking on
you here, but I do see a lot of misguided theories in Mac troubleshooting,
and it doesn't always help people in similar situations to have too many
half-formed notions kicking around.
> --In these situations, completely drain the PRAM battery before PRAM and
> Power Manager resets and before concluding on a dead MB/CPU.
Absolutely key. Even better is to pull the motherboard battery, but that
does require opening the machine. The little-dutch-boy maneuver (holding
the reset button down ad nauseum) should really do the same thing without
need of discharging the battery, but it's physically difficult to do and
it may not even be implemented on the 2400 (no mention in the manual?),
both of which further exacerbate the problem of voodoo diagnosis.
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