External display problem

Hello

I have an iMac 2006, this model: http://www.everymac.com/systems/apple/imac/specs/imac-core-2-duo-2.0-17-inch-specs.html

The display is messed up, so I use an external 1080p display, this one: http://www.viewsonic.com/us/vx2450wm-led.html

I use mini-dvi-DVI adaptor and a DVI cable.

The problem: 1920 x 1080 screen does not fill the screen, but there are 2,5 cm black bar on the sides. The resolution setting says 1920 x 1080 though so it should be fine.

With an old Mac mini (http://www.everymac.com/systems/apple/mac_mini/specs/mac-mini-core-2-duo-1.83-specs.html) it works fine but I don't want to use that one, it's slower than the iMac.

Any idea why there is this problem with the iMac?

Thanks a lot!!!

 

Well, it says on everymac about this iMac:

Details: Apple reports that this model supports "digital resolutions up to 1920x1200" and "analog resolutions up to 2048x1536".

Doesn't that mean that it should also support 1920x1080? Or have I misunderstood something?

And about that Mac Mini it says the very same thing: The DVI video output supports digital resolutions up to 1920x1200.

So why does it work with Mini but not with the iMac? I don't get it.

 

As an extended desktop it IS fullscreen on this external display like it should - but when I mirror it, then the black bars come.... ?!?

 

Yeah, I got it know, it was a silly question..