switching monitors

[Ken Grunke]

I've been using a dinky 14 inch monitor on my PM7500, and just got an old Radius
21 inch color display and an equally old Radius Thunder PCI video card to drive
it. Works beautifully on MacOS.
The Radius only shows the first block of start-up text after "Welcome to Linux",
after which the original monitor on built-in video takes over with the YDL 2.2
startup.
Seems like a good sign to me, I should get the monitor to be recognized in YDL,
but don't know how.
I looked at the how-to on configuring dual monitors, it was over my head and
seemed to apply to only the Rage 128 card.
I tried the Radius without the original monitor, using both built-in and video
card output. it was the same--no startup. The built-in video is not enough to
drive the Radius monitor, anyway.
Then I tried going into install mode from BootX by checking the box for text
ramdisk in the BootX options, exactly the same thing.
Ideally, a dual-monitor setup would be great, but if I can get just the Radius
21 inch monitor to work on YDL, I'd be very happy.
I'm a command-line newbie, can someone help me get this monitor going please?

Ken