[Tfug] Battery replacement

[Bexley Hall]

> Well,
>        Powering down the machine, and removing the
> battery means that
> the CMOS configuration will get wiped out. Then the
> box becomes a
> paperweight or a doorstop, or you can decorate your
> fireplace mantle
> with the motherboard.

Possibly. Depends on the technology used to implement
it, how much bulk decoupling there is local to the
chip, how LONG you take to swap the battery, etc.
I know that when I write RAM tests for CMOS devices,
I have to put in VERY long delays (minutes) to
eliminate the effects of residual charge remaining
in the memory cells AFTER power has been cycled, etc.

If you truly fear trashing the CMOS -- and don't think
you can restore ALL of it using the SETUP (BIOS, etc.)
-- then drag out a DOS boot floppy and use
DEBUG to examine the contents of the RAM *before*
you swap the battery.  You can similarly restore
the contents after replacing the battery before
trying to reboot to disk.

Note you need to see just how big your RAM actually
is if you want to be sure to get ALL of it saved
(the original "CMOS" was only a hundred bytes;
nowadays, there are hidden pages of memory used
to store extended configuration data)

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