Failing chips (was '91 200Q vs. S4/6)

[Linus Toy <linust@mindspring.com>]

Henry Harper noted--

>For a little non-Audi content. Dad's other-German-car 944T is cutting =
>boost on him while on longer drives, restorable temporarily by cycling =
>the key, he says. Claims this is typical of failing semiconductor =
>devices and wants to blame new chips from PowerHaus. Should I
>explain that the chips are just lookup tables, 

well....in fact, heat CAN and DOES affect EPROM chips, and the Motronic
brains in our cars ('91 200q/S4/S6/951) generate some serious heat.  When I
upgraded my '91 200q ECU to IA stage III, Ned could not properly erase one
of the original Intel EPROMs (there are two of them, and one of them erased
all but the first bit), so he used one from his stock of compatible EPROMs.
 It did not cut it.  I don't recall the manufacturer, but the summary is:
the OE Intel chip is an automotive grade chip; the replacement chip Ned
tried to use was an industrial grade chip.  Although designed to tolerate
harsher conditions than "consumer" grade chips (i.e. for PCs, stereos,
etc), the industrial grade chip would fail from heat after about 30 minutes
of sustained running.  Ned eventually used another Intel chip and the heat
problems went away.

Note that this may be unique to the computer in my car (he'd never had an
EPROM erase like that either)--Ned has successfully used the industrial
grade chips in other '91 200q upgrades.

HTH
--Linus
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* linus toy                       email:  linust@mindspring.com      *
* mercer island, wa                                                  *
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