Sounds like a PRAM battery issue to me. The 6100 is a hard-power computer, so they are more affected by bad PRAM batteries than soft-power models.

Here's a quick way to (probably) get the machine up:

1. Turn it on.

2. There is a reset button (marked by a triangle in a circle), and a programmer's button (a little wavy bump thing in a circle), on the back right-side of the computer. A few seconds after the chime, press the reset button once. The computer should chime again and take you to the grey screen.

3. Insert a system disk of some type (CD/floppy/spare HD) for the machine to boot from.

That should do it.