Magnum hardware questions

[nathanw%MIT.EDU@localhost (Nathan J. Williams)]

[Is this thing on?]

I just picked up a Magnum 3000 box from a lab; the tag on the back
says it's a model M/20.

It has a color framebuffer, 24 SIMMs (1M each, I assume?) and two
disks.

I hooked up a serial cable and powered it up; the output I get is:

nvram: invalid checksum
tod clock being kickstarted!

and then nothing. Doesn't respond to return, BREAK, etc.

I see that the clock chip is the infamous MK48T02. I have a few spares
of this part. Is it likely to help anything if I replace it? And if I
were to do so, is it easier to remove the power supply from the system
to get access to that part of the system board, or to somehow pull the
system board out of the case?

Any other ideas for what to do with this box would be appreciated, as
well as information about where a 3000 M/20 fits in the scheme of things.

        - Natbab