>  I have one in a 5000/200.  The PROM recognizes it as a PrestoServe
>non-volatile memory, but I do not know how it does it.

I _think_ I do, but I'm not completely sure...

>  I have been working on a modified memory sizer code, and have it
>recognizing non-contiguous memory and a hack to not include the PresotServe
>memory in the NetBSD memory list.

Neato. 

There's also the hairy question of figuring out the battery status
(which you need to in order know if the NVRAM contents is good),
figuring out just how much NVRAM there is (IIRC, there were two sizes
of board), and then checking the signature in the NVRAM.
Plus maybe fiddling around with enabling charging/online mode,
vs. going to standby (low-power mode), i forget.

And then there's the same all over again for the 5100.
Simon Burge has a couple of those with  NVRAM boards.