3 Monitors MiniDisplayPort-VGA black border problem

[frankyboy]

Hello,
finally i got 3x 24" monitors for my Mac Pro.

Monitor 1: DVI - DVI
Monitor 2: Minidisplayport - VGA Adapter > VGA
Monitor 2: Minidisplayport - VGA Adapter > VGA

it works but strangely there's a 3cm black border on both screens with MDP-VGA Adapter but only on the left side each.

on the AOC monitors i've already tweaked the screen settings manually but there's still those 3cm black border on both screens.

does anyone got a trick to solve this problem? any settings in OSX or maybe a tool?

Setup: Mac Pro / Ati Radeon HD 5770 / OSX 10.6.8 / AOC 2436

thanks for any help in advance.

 

[alphaod]

Are you using 'Active' miniDP adapters?

Something like this:
http://www.amazon.com/Cirago-DisplayPort-Active-Adapter-DPA2011/dp/B005AT2KTK

I know with DVI if you don't use active adapters, you can't use the DVI and both miniDP ports, so I imagine it's a similar issue with VGA.

(The Apple-branded adapter is passive)

 

[frankyboy]

Yes, i'm using quite similar adapters but the original Apple miniDP to VGA adapters which are also 'Active' adapters.
usually they should work as i've seen others on the apple forum doing the same but none of them got this border problem. i suppose it's the monitors screen settings which aren't big enough to fill that 3cm black border on the left.

i might buy a second graphic-card to use DVI only if i cannot fix that problem.

thanks anyway for your answer.