Vertical lines on dual display after boot up with NVIDIA GeForce 6600 on G5

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Level 1

8 points

Vertical lines on dual display after boot up with NVIDIA GeForce 6600 on G5

I have just upgraded my G5 Quad from OS 10.4 to OS 10.5. Now, whenever I boot up the dual display is split into vertical stripes. I can fix it for that session by unplugging one monitor and plugging it back in again. If I boot up from the 10.5 install disc - same problem. If I boot up from the 10.4 install disc - works fine. The display does not go into vertical segments during the grey start up period, but only when the desktop appears. Anyone got any ideas?

G5, Mac OS X (10.5.6), NVIDIA GeForce 6600

Posted on Jun 24, 2010 1:51 PM

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Answer 1

BDAqua

Level 10

238,973 points

Jun 24, 2010 3:16 PM in response to cpettit

Have you done a PRAM reset, CMD Option+pr...

http://docs.info.apple.com/article.html?artnum=2238

Does it boot into Open Firmware with CMD Option+of ?

http://docs.info.apple.com/article.html?artnum=42642

reset-nvram (press Enter)
set-defaults (press Enter)
reset-all (press Enter)

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Answer 2

cpettit Author

Level 1

8 points

Jun 24, 2010 11:57 PM in response to BDAqua

Thanks for these suggestions. I have tried both but neither cures the problem.

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Answer 3

BDAqua

Level 10

238,973 points

Jun 27, 2010 6:11 PM in response to cpettit

Safe Boot from the HD, (holding Shift key down at bootup), it will try to repair your Disk Directory while the spinning radian is happening, so let it go.

Does it happen there in Safe Mode?

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Answer 4

cpettit Author

Level 1

8 points

Jun 28, 2010 2:34 AM in response to BDAqua

Just the same in safe mode. My workaround is to pull one of the monitors out and plug it straight pack in again but I am concerned this this might damage the card. I am surprised that no one else has reported this problem. Could it be something to do with the monitors I use (Lacie photon20vision) or the resolution setting (1600x1200)?

If I change the setting to 1344x1008 it will boot up fine. I can then change the settings to 1600x1200 and carry on working at this resolution.

So I now have 2 workarounds (re-plug one monitor or reset the resolution) but neither is ideal.

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Answer 5

japamac

Level 7

24,400 points

Jun 28, 2010 3:58 AM in response to cpettit

Hi-

I think what you are seeing is a result of poor, possibly failing, VRAM.

The stripes sound very typical of VRAM errors, and the fact that dual monitors in Leopard are added to the mix furthers the theory.

Leopard uses the graphics card much more than Tiger, that is, pulls more resources (power) from the graphics card.
Add the load of two monitors at relative high resolution, and marginal VRAM can exhibit symtoms of being so; marginal.

I'm curious as to a possible third work around. If the monitors are equipped with power buttons, does cycling one off, then on, allow proper display at the desired resolution?

Also, is this Geforce 6600 the 128MB version, or the 256MB version? This is listed in the System Profiler/Graphics/Displays.

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Answer 6

cpettit Author

Level 1

8 points

Jun 29, 2010 12:03 AM in response to japamac

Hi

No, turning off the monitor's power button does not have the same effect as unplugging it.

The VRAM is 256MB.

Having reset the displays to 1600x1200 yesterday (after a good boot up at 1344x1008), when I booted up this morning all is well!

Only one successful boot up but maybe the problem is solved - for now.

Thanks for your help.

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