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AMD 5770 stuttering with clean install Mountain Lion

I am having issues with bad screen stuttering using an AMD Radeon HD5770 on my early 2008 3,1 Mac Pro running two 24" Apple Cinema Display in portrait mode. The screen stutter/shaking issue is very obvious when using animations like alternating between Spaces/Desktops.


This issue does not occur using the Mac Pro's original ATI Radeon HD 2600 XT.


I do not think the HD5770 graphics card is to blame because the issue does not occur when I boot into my legacy internal hard drive, which over the years I have updated from OS X 10.4 Tiger to Mountain Lion.

FYI- I had previously used an ATI Radeon HD3870 with that drive...is it possible there are old AMD drivers enabling the HD5770 to work?


The screen stutter issue only occurs when I have booted to a clean install of Mountain Lion on my OWC Mercury Accelsior PCIe SSD. Is it possible that booting onto the PCIe SSD is interfering with the HD5770? I LOVE this SSD card and really want to continue using it as my boot drive, so I'd like to figure out how to enable it to work with this graphics card.


Since Mountain Lion includes the HD5770 drivers, I am perplexed why a clean install would not work but the upgraded system does.

Since there are no drivers to install, I have reached an impasse with my clean install of OS X 10.8.


Any thoughts how to troubleshoot this?

Mac Pro, OS X Mountain Lion, Mercury Accelsior PCIe; HD5770

Posted on Aug 20, 2012 8:53 AM

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Posted on Aug 21, 2012 3:18 AM

Clarification:

After further investigation, it turns out that my working legacy installation is Lion, not Mountain Lion.

So my conclusion is that the HD5770 using OS X 10.8 Mountain Lion is currently incompatible with my portrait dual head ACD set-up on a 2008 Mac Pro.

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AMD 5770 stuttering with clean install Mountain Lion

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