Anyone have any experience replacing a Dallas 1287 with a 12887?

From: Dwight K. Elvey <>
Date: Tue Dec 31 17:49:00 2002

>From: "Ethan Dicks" <>
>While attempting to revive a Compaq 286/SLT laptop for use as a
>front-end for my UP600a programmer, I have found that the battery
>on the DS1287 has died (no suprise there). What sucks is that
>even after I run the floppy-based setup utility, after a reboot
>(not a power-off cycle), the machine forgets what I just set,
>both the data and time, and the geometry of the A: drive. Seeing
>as how it thinks there's a 5.25" floppy and it's really a 3.5"
>high-density drive at the end of the cable, as you can imagine,
>it won't reliably read disks.
>So... I have ordered a replacement DS12887 since they no longer make/ship
>the DS1287. Couple of interesting app notes here:
>What I'm wondering is if anyone on the list has ever replaced a DS1287
>with a DS12887. One of the sheets seems to suggest that I'll need
>an updated BIOS ROM (clearly not available for a 286 laptop) to drive
>the extra stuff associated with the enhanced century rollover.
>Alternatively, has anyone here successfully performed surgery on a Dallas
>module? I have disconnected the battery from a Mostek 48T02 from a SPARC
>and soldered on an external Lithium cell, but the packaging makes it easy
>to get access to the battery wires coming down from the top (I even put
>the battery on a 9V battery snap so it's easier to replace) I haven't
>heard of anyone doing this for the more sealed Dallas modules.
>So... anybody else suffer though this?

 In a search of the news groups, I found an article by a fellow
that had done surgery on a number of different modules. One thing
that seemed to be constant was that they put the battery in
a number of different locations within these types of devices.
If I was going to hack mine, I first take it to a printed circuit
building shop. These guys usually have a small X-ray machine for
inspecting solder joints. With one of these, you can locate where
the vital parts of the chip are. You can then use a Dremel to grind
into it and connect an external 3V cell.
Received on Tue Dec 31 2002 - 17:49:00 GMT

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