2 Dec
1998
2 Dec
'98
10:02 a.m.
Once upon a midnight dreary, R. Stricklin (kjaeros) had spoken clearly:
On Wed, 2 Dec 1998, Tony Duell wrote:
If the markings are for a Dallas 12887(a) then the NVRAM is integrated with
the clock chip & battery. To my knowledge, the closest person to being
world-famous for changing a Dallas battery would be Dr. Marty Goodman, of
CoCo fame. IIRC, he's a member of a mailing list gatewayed to the newsgroup
bit.listserv.coco, so if you send a message there, he should eventually get
it (along with everyone else on the gatewayed list, so pose it as a
CoCo-ish question... tho CoCoists (IMHO) aren't quite as rabid as some
other platform gurus...)
If the RTC chip is much taller than the other
chips on the mainboard (say
about 3/8" high) then it probably contains an internal battery. Dallas
and Mostek/SGS-Thomson made chips like that.
It is. I forget offhand who made it, though. Would it be powering the
NVRAM, though? On a SPARCstation you actually have to replace the NVRAM
chip itself. I guess it couldn't hurt to try to replace it. > You're supposed to replace the chip when the
battery fails (after about
> 10 years). I have heard of people carefully slicing the top off the
> package and replacing the lithium cell inside, but I've not had to do
> this myself - yet.
If it is a Dallas 12887 (without the "A" suffix), I can tell you this:
beware of the Dallas 12887. The 12887 has one shortcoming: the NVRAM
*cannot* be reset via external means, which means if whatever machine has
fouled the NVRAM so badly it can't boot, it'll *never* boot again without
replacing the chip itself. Some PC's used this chip, and said machines are
a thorn-in-the-side when their NVRAM settings go haywire.
IIRC, the Dallas 12887A is pin compatible, and *does* have an NVRAM reset
pin... I also know that you can get all the pin info & other stuff from
Dallas's website, which is slightly confusing at: http://www.dalsemi.com/
Watch out, tho: All their datasheets are in PDF format, so you'll want to
grab Adobe's Acrobat reader to view the sheets with.
The page with all of their PDF's for their chips is:
http://www.dalsemi.com/DocControl/PDFs/pdfindex.html
Hope this helps,
Roger "Merch" Merchberger