Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: 80287 speed question and heat sink glue???
Message-ID: <1989Dec28.232038.12482@utzoo.uucp>
Organization: U of Toronto Zoology
References: <1716@rex.cs.tulane.edu>
Date: Thu, 28 Dec 89 23:20:38 GMT

In article <1716@rex.cs.tulane.edu> hoang@rex.cs.tulane.edu (Dzung Hoang) writes:
>...The 287 is now running at 12MHz, a little over
>the 10Mhz the chip is rated for and above the CPU's 10Mhz.
>
>    Is running the 287 above its rated speed harmful or dangerous? ...

It will probably increase power consumption and heat dissipation, but
probably not enough to cause trouble unless the design was marginal to
start with (which is possible...).  More to the point, though, is the
question of whether you can trust the answers you get out of the chip.
The chips marked "10MHz" are generally the ones that flunked the tests
at 12MHz (or whatever the next speed grade is).  Now, those tests are
a bit conservative, and depending on things like supply voltage and
temperature, you may not have trouble.  Then again, you might.  Worse,
if the chip is right on the edge, then when something changes a little
bit -- room temperature, power-line voltage, component aging, phase of
the Moon -- you could start getting intermittent failures.  I wouldn't
trust it for anything crucial.
-- 
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1989: birds nesting in engines | uunet!attcan!utzoo!henry henry@zoo.toronto.edu