Mac Pro 4870 Freezing & Stuttering

I apologize for the poor quality, as this was taken with a handheld photo camera not a video camera.

This is an example of the stuttering documented in this Apple support thread: http://discussions.apple.com/thread.jspa?threadID=2130243&tstart=0

This problem is most visible during the Flurry screen saver. However, users will experience the mouse cursor not fluidly moving around the screen and freezing.

This problem appears to affect Mac Pros with the 4870 graphics card. For my situation it only is caused when the secondary monitor is turned off but still connected via DVI cable. The system acts as if the second monitor is still active even when the monitor is powered off. This is causing the system to freeze and stutter. Only after the DVI cable is unplugged does the system resume normal functionality.

System Specs:
Mac Pro Quad Core 2.93 (Early 2009)
Snow Leopard 10.6.2
Primary Monitor (right): 24" LED Apple Cinema Display
Second Monitor (left): 24" Samsung SyncMaster 2343

Category:

Science & Technology

Tags:

• Technology
• Apple
• Mac
• Pro
• Stuttering
• Mouse
• Freeze
• Freezing
• 4870

[FourLiterV8]

Do you know of a solution to this issue? My 24" iMac has the same problem.

[Lichach]

@FourLiterV8 Do you have an external monitor hooked up to your iMac? This situation only happens when I have my secondary monitor hooked up but turned off. It appears to be a handshaking issue with the GPU. If it is happening to your main iMac monitor (without a secondary monitor), I'd recommend going to an Apple store to have them investigate.

[AttackTheMic]

Anyone figured out how to fix this yet?

[LoonyMcAnal]

The issue seems to occur on most ATI based Macintosh systems with a multiple monitor setup. The issue of stuttering only occurs if you turn off or "disable" one of the displays. When I say "disable", I mean using a piece of software such as SwitchResX. SwitchResX gives you the ability to disable one of the displays without actually unplugging it, however this still causes the stuttering issue. I have yet to find a way to fix it and Apple just seems to ignore the issue.

Can anyone help?

[FourLiterV8]

Yes, my problem is the same as yours. It only occurs when my external monitor is hooked up but turned off.