Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!wuarchive!cs.utexas.edu!rutgers!njin!princeton!njsmu!mccc!pjh
From: pjh@mccc.uucp (Pete Holsberg)
Newsgroups: comp.sys.ibm.pc
Subject: Re: engineering margins (or, living on the edge...)
Message-ID: <1989Nov12.154710.25669@mccc.uucp>
Date: 12 Nov 89 15:47:10 GMT
References: <1989Nov10.214341.4071@ico.isc.com>
Reply-To: pjh@mccc.UUCP (Pete Holsberg)
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Organization: The College On The Other Side of U. S. Route 1
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My experience in manufacturing electronic components (granted, it was a
long time ago) suggests that reliability is not guaranteed no matter
what.  A manufacturer tests a part say for speed, and on the basis of
actual performance, places each device into a separate category.  For
example, if a 386 performs OK during the 25 MHz test, it's marked
"25MHz",  If not, it's tested for 20MHz, etc.  To be sure, some kind of
life testing is usually done to ensure that the test itself is reliable.
 But on the other hand, I'll bet that testing is done statistically,
i.e., a sample of a batch of devices is tested and on the basis of the
test results, the entire batch is categorized.

Perhaps the safest approach is to derate the parts: use a 25MHz part at
20MHz, just to be sure that "drift" never gets you in trouble during the
lifetime of the device.

-- 
Pete Holsberg                UUCP: {...!rutgers!}princeton!mccc!pjh
Mercer College               CompuServe: 70240,334
1200 Old Trenton Road        GEnie: PJHOLSBERG
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