Ace & Security

From: Roger Merchberger <zmerch_at_30below.com>
Date: Tue Sep 28 18:06:02 1999

Rumor has it that Dwight Elvey may have mentioned these words:
>ard_at_p850ug1.demon.co.uk (Tony Duell) wrote:
>>
>> Well, what if the NVRAM is one of those Dallas devices with the battery,
>> clock/NVRAM chip and crystal encapsulated in the same package. No easy
>> way to pull a jumper and clear those.
>
>Hi
> Most of the ones I've seen used in computers are the normal
>NVRAM's that Dallas sells. These have no security bits or
>special access codes. To a system, they look just like
>comparable sized CMOS RAMs. They can even be plugged into
>the same sockets.
>Dwight

Ah... depends on the Dallas device. The two main devices used on (older)
motherboards are the 12887 and the 12887A.

Anyone care to take a guess as to the difference?

The 12887A has a "erase" pin on the package, so even if there are no
jumpers on the motherboard to erase the CMOS, you can jumper that pin to
ground for a few seconds and Voila! Wiped settings.

The reason for the "A"? The 12887 had _no_ pin for erasure, and if you
forgot your CMOS password, or your CMOS got jumbled, you're SOL. (That's
Surely Outta Luck... ;-) Many of the cheaper motherboard manufacturers
soldered that package to the board, as well... meaning if you wanted to use
that motherboard, either desolder that chip, install a socket, then put in
a 12887A, or wait 10+ years for the battery to die. (even for that, the
board's close to useless... once you turn off the 'puter, it'll forget all
your CMOS settings.)

PDF's of those parts are available from Dallas's website, which IIRC is
http://www.dalsemi.com/

HTH,
Roger "Merch" Merchberger
--
Roger "Merch" Merchberger   ---   sysadmin, Iceberg Computers
Recycling is good, right???  Ok, so I'll recycle an old .sig.
If at first you don't succeed, nuclear warhead
disarmament should *not* be your first career choice.
Received on Tue Sep 28 1999 - 18:06:02 BST

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