IBM RS/6000 - more trouble or just my terminal?

Hi! I'm new to the *BSDs. I have a couple of IBM RS/6000 43P 140s that
I would like to get set up with NetBSD, so that I can port some of my
software to the platform, as well as turn away from using my old
StarMax Mac clone as a server.

I've been reading through the mailing list for the month of January,
and it looks like I'm coming into the scene just about at the right
moment.

So, here's my problem. I've got my test machine booting onto the
installation_com (being that my machines don't have any VGA cards)
diskette, and I'm able to mount the prep ISO disc that I burned to a
CD, using "mount -t cd9660 /dev/cd0a /mnt". I would rather not use
netboot, since that whole idea is quite clunky IMHO, especially since
I would have to go through the trouble of setting up NFS and stuff.

Anyways, when I try loading up the "sysinst" program, my terminal
seems to go dead: the cursor goes to the top-left-most position and it
appears as though that all input from the machine is getting sent only
to the bottom-right most character position, so I am of course unable
to proceed because I can't see a thing!

I have a similar problem immediately after booting; when it asks me if
I want to exit to shell, if I were to pick install, it will do the
exact same thing. If I pick to go to the shell, it will go to the
shell almost correctly; the shell displays fine, but the screen does
not refresh, so I still see all of the old initialization stuff from
before. I hold tab down for a while to clear the screen as a solution
to clearing all of the junk out.

What's even worse is that once the terminal seems to get into such a
state, whereas the cursor is in the top-left and only the bottom-right
gets updated, it stays that way even after a reboot which leads me to
think that maybe it's a terminal problem? If that's the case, then
will my ATI Rage 128 card work to get a VGA card into it?