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List:       classiccmp
Subject:    Re: More Apple II fun - 4116's
From:       "Tim  Shoppa" <tshoppa () wmata ! com>
Date:       2009-04-30 17:27:32
Message-ID: 49F9A7440200003700053DF3 () gwiavs ! nservices ! wmata ! com
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Mike asks:
> My real question is - 9 faulty out of 48, spread across both machines,
> seems very high. Are 4116s that unreliable? Or perhaps they're quite
> sensitive to power supply problems?

It isn't unusual to find that many years after manufacture, that a
particular batch of DRAM chips aren't reliable anymore.

DEC and other memory board makers used to keep internal lists
of known good batches and known bad batches of chips, and even
kept track of what brand/batch are shipped with each memory board
for long-term reliability tracking.

But it seems more likely that something marginal in the timing of the
motherboards or the power supply or something else is causing your
observed flakiness.

I don't really understand what you mean about the Apple II's "wouldn't
boot", though. They do not do an extensive (or any!) power-on memory test
but maybe loading DOS 3.3 is hitting RAM hard enough at power on
that it's turning somethng else up. As others have noted, just going
into BASIC at power-up doesn't hit memory too hard, and the quickie
tests of going into hi-res graphics and looking for flakiness on the screen
is useful if not definitive.

Tim.


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