Mac Pro lags since I connected a 2nd monitor - HELP!!

[RickUnique]

Hey guys,

I just bought a 2nd monitor and i have lags every 5 seconds which
last about half a second (feels like 10 or less fps during the lag).
It happens with all kinds of applications. It gets worse with multiple
applications openend at a time. The crazy thing is that it only occurs
when i start to use both monitors at the same time. When i e.g. use
Logic 9.1 and use one monitor everything runs nice and smoothely
but as soon as i move the window slowly to the 2nd monitor i can
see the window lagging while I'm moving it. This is really annoying
because it seems not every input from the mouse/keyboard gets
into the system and its not a smooth workflow at all.
I switched the monitors connections but it didn't help.

Mac Pro (Early 2008) 2.8Ghz 8-core
Snow Leopoard ( 10.6.2 )
6GB RAM (2x2gb kingston, and the usual 2x1gb)
ATI 2600XT and 3 HDD.
1 Monitor 24" running at 1920 x 1200
1 Monitor 22" running at 1680 x 1050

I really hope that you guys can help me out with this one.
What coule be the problem? The ATI 2600XT should definately
be able to handle two screens at one with such little graphics
in logic 9 ?!

I want to run Logic 9 and an analyzer software (spectre from AE)
at the same time but its not possible with the LAG.

The problem/lags also occur when i sync the monitors.

Could the RAMs be a problem ?
Would a 2nd graphics card be a solution? But as I said
before its not a graphics demanding application.
Is it a hardware or software "error"?

Summary:
- The whole System lags (not just one monitor) when
I start to use both monitors (having application windows on both).


Thank you in advance for your help guys!

Rick

 

[ljonesj]

i dont know if this will help but try it run both moniters with the same resolution like 800x600 on both for example that may help and make sure both have the same refresh rate on both

 

[kellen]

Something sounds off, I ran dual 23" with the 2600 for some time, both at 1920x1200.

 

[RickUnique]

Hey guys !

Thanks for your Tips.
Unfortunately I was'nt able to fix.

@ljonesj

I tried running both monitors with a resolution of 1024 x 8xx but it didn't
change things - maybe it was a tiny little bit better than with the standard
resolution. Both have a refresh rate of 60Hz. One Monitor says "60Hz(NTSC)"
and the other just "60Hz" but that should be the same.

@kellen

What kind of applications are you runnin
Anyone else any recommendations ? Is my only chance buying a new graphics
card like the ATI 4870 ? damn 3xx is quite a price for running a 2nd monitor
while already having 2 DVI connections.



Even with the safari window I get some lags while I am moving it in from one
monitor to the other. It is just noticeable - not as bad as with the Logic Pro
window or some other """"graphics demanding""" application.
I am - lets say a little bit - "addicted" to a smooth workflow and I even feel
very little lags on the system.

Hope somebody enlightens me or my mac pro with some good advice !

Rick