Last night, i finally went ahead and connect my 20" iMac to my 42px60u Panasonic plasma.

I have it connected MiniDVI->DVI-HDMI Cable->XtremeHD HDMI Switch->TV.

Everything went fine, except that when setting the iMac to 'mirror' the display, I could not find an appropriate resolution for the TV in order to fill the entire screen. Most I could get was that the display was a bit too big for the TV and it couldn't fit the whole desktop. This also caused the iMac to match the display of the TV, which didn't fit the 20" iMac display very well either.

When I unchecked the 'mirror' option, the background from my iMac now filled the whole screen, only problem is that the iMac is in the other room, so I can't see what is going on in the main screen.

What resolution should the output to the TV be set at so it fills the screen appropriately?

It's always best to try the native res of the display first, so for that plasma, maybe 1024 x 768? Look it up to be sure.

im pretty sure i remember looking for that but it not being an option. ill have to check again.

Would it help if, with mirroring unchecked, the iMac was the display with the blank background image and the Panasonic was the main screen? If that would work for you, that can definitely be done under the Arrangement tab in Displays preferences (by moving the little white menu bar from one screen to the other).

that's a great idea. ill have to try and work that out. thanks!

so, i went ahead and tried it, but still cant get a good fit - if the display fills the screen, the very top and bottom of the screen is cut off (about half of the menu bar is missing) and if the entire screen fits (no cutting off), then it doesnt fill the screen on the TV.

im curious to hear from other folks that have done this and what their settings are. i was hoping not to have to purchase an additional PC to run internet content to this TV, but it looks like i may have to...

it would appear that the issue i am seeing is here -

http://www.avsforum.com/avs-vb/archive/index.php/t-872194.html

will all PC output devices have this same problem?

Yes, a PC will have the same problem. You could try using SwitchRes X to build that listed timing (1248 x 700) and see if that works.

so, i went ahead and tried it, but still cant get a good fit - if the display fills the screen, the very top and bottom of the screen is cut off (about half of the menu bar is missing) and if the entire screen fits (no cutting off), then it doesnt fill the screen on the TV.

Sounds like you're pretty close right now. It could be as simple as turning off "Overscan". That will shrink the picture slightly. Overscan is in the "Options" of the Displays Preferences.

i tried switchres x, but it didnt seem to change the output at all, even when choosing a custom output resolution.

i will check again, but i think unchecking overscan make it almost like a 4:3 resolution.

actually, what is happening is this - whenever the output resolution to the TV is tuned to anything other than 1920x1080, the resolution on the iMac changes to something other than its default of 1680x1050, which is extremely annoying. I would like to keep the TV output plugged in all the time, but can't see doing it that way if it is now changing the resolution of the iMac screen. Anyone know why it does that?