05-11-2006, 10:26 PM

I purchased an iMac back at the start of this year as an "Upgrade" from my three year old 17-inch PowerBook. Only after I purchased it did I find out that unlike the PowerBook it didn’t support a split image when plugged into another monitor, only a mirror image.

So I installed “Screen Spanning Doctor”, an excellent application that allowed this to occur.

Now I have both the PowerBook and my iMac attached to a 21-inch Dell Trinitron.

Problem is, the PowerBook (DVI out, converted to VGA) gives a beautiful picture, but the iMac image has ghosting, particularly noticeable to the right of black letters on a white background. It seems to be least at 60Hz.

I have tried swapping the cables, but the same thing happens, and these are good quality cables. The output is an Apple adaptor from the video out port, and swapping the VGA cables between PowerBook and iMac has had no effect. The PowerBook output is perfect.

This is highly frustrating, and consequently, I am still using my PowerBook as my main computer. Does anyone know how to fix the ghosting on the output from an iMac?

05-12-2006, 12:20 AM

screen spanning hacks split up the video RAM between the screens, how much is on the iMac?

05-12-2006, 05:03 AM

This is Purple Thumb here - who had problems with my Purple Thumb account, and had to re-register to answer the question posed.

The iMac is running at LCD 1680 x 1050, and the DELL 1600 x 1200 at 60Hz. The video RAM is 128mB. Is there a way to bump it up? Overall I have 1.5 GB DDR SDRAM.

The ghosting continues to occur even at lower resolution on the second monitor though...