(By the way this happens with Mac OS 8, not Mac OS 9 which fixed it)
I have this nice little 17" Sony multiscan Trinitron. Just got it. Works great. I love it, kind of.
When I got it, the specs said it would do 1024x768. Yum, just what I'd like for surfing the net.
Put it on my 7200 PPC, booted up. Things looked kind of big, too big to be a real 1024 by 768.
Looked at the resolution with system 8's nifty little Control Strip and aha, it was only set at 832 x 624. Well that's easy enough, just bump it up to the 1024 x 768 setting and everything will be great. WRONG!
What a disaster, the monitor had this big white 3 inch horizontal strip right down the middle on a black background so none of the screen can be read to change the setting back.
Rebooting doesn't help one bit.
Rebooting using the shift key to turn extentions off doesn't help one bit.
Zapping the PRAM begins to look promising but things jump back to the white band in a few seconds.
Zapping the PRAM twice and turning off extensions gets me to the desktop.
But there is still a new secret to discover. The settings are stored in two places, not one, if you change the resolution with Control Strip or the Monitor control panel.
You can either make the resolution change when you get to the desktop or you can dump both the Finder preferences and the Display preferences in the trash. Unlike System 7.5.5 which only updates the Display preferences, file System 8.0 changes both files. In any case you will end up rebooting. If you only erase one of them, you're back in the same soup.
If you are so unlucky as to follow in my footsteps, you might want to know that it really is necessary to zap the PRAM twice on a Power PC model because there are two PRAMs in the PPC. One is the old standby and the other is a newer one called NVRAM. It is very important to press the opt-cmd-p-r combination to zap the PRAMs immediately after startup begins and to continue holding them down until you have heard it chime twice. If you have trouble booting without unplugging your machine try pressing command-control-startup on your keyboard.
You may be able to temporarily get to the web to read this by installing a different monitor on your machine or booting off something else after a zap, but in the end there really are four different things that simultaneously go wrong. A real diagnostic nightmare. Hope this little writeup did you some good.
Now I feel cheated. So do lots of other people. This is not at all uncommon. There are lots of makes and models of multisync monitors out there that are only partially Macintosh compatible. The older they are, the more likely the problem. I've seen NECs and HPs work a lot more often than others. The word multisync is not descriptive enough. It comes in many flavors, a small range of fixed values vs a much larger range compatible with a broad line of products. The bigger the monitor, the more likely it will need some special card. If the monitor is old or the company is out of business, you may find that the monitor is totally unusable on a Power Mac with a PCI bus. If you don't ask specifically which resolutions on the spec sheet apply to your Macintosh, you get to find out the hard way when you get it home. It is extremely common for there to be "no known Macintosh video card available" for many of the new high resolution monitors currently being sold! I was "lucky", there was a third party card that worked for me. A word to the wise.
There is this nice little monitor database that you can look at Monitor Database and Compatibility Lists
Another Monitor Database and adapter from a company in France
Monitor Resolution Solution A helpful page that might solve your monitor problems.
Startup key combinations to reset the resolution on third party video boards:
SuperMac (at least some models)press&hold OPT
Imagine 128 Card (reset resolution) N
RasterOps (at least some models)press&hold CMD-OPT-SHIFT
Radius (Use cable sense pins to set resolution) U
Radius (Cycle through available resolutions) T
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