Is my Mac's video card about to die?
January 3, 2011 4:43 AM   Subscribe

Text on my Mac pro's monitor is behaving oddly, with intermittent horizontal bars of static across the lines of text. I think it might be the video card. Is it about to die?

The windows on my main monitor are occasionally interrupted by horizontal bars of static across the text (I don't think pictures are affected). The bars start and end at the edges of the affected window and they stay on their row of text as I scroll the contents of the window up and down. The bars move with the window if I move it around, but they go away if I move the window onto a different monitor and - bizarrely - don't reappear until the window has re-entered the main monitor by more than about a third of its width. Making the window more narrow seems to help too.

I'm using a Mac Pro 1.1 running OS X 10.5.8. I have two monitors. The one which has the problems (I haven't seen the problem on the other one) is a Dell U3011. Both monitors are driven by an ATI Radeon HD 4870. I've tried rebooting and clearing caches. Can I try anything else to fix the problem, and should I replace the video card pre-emptively?
posted by Joe in Australia to Computers & Internet (7 answers total) 1 user marked this as a favorite
• Re-plug the monitor into the card.
• Re-seat the card in the MacPro. While you have card out of the MacPro, clean all the dust off it with a can of air.
• Swap the monitors. That is, switch which port they're plugged into. If the problem now shows up in the second monitor, it's definitely the card.
posted by Thorzdad at 5:07 AM on January 3, 2011

Try swapping the ports the monitors are plugged into. This will help isolate the problem either to the video card (or operating system), or to the Dell monitor.

If you then need to discriminate the problem between the video card and OS, boot from an OS X installation DVD (such as the one which shipped with the Mac Pro) and see if you can replicate the issue.

If you see the same problem, you have a hardware issue, which is most likely the video adapter. You would either replace this under warranty or just replace on your own.
posted by Blazecock Pileon at 5:09 AM on January 3, 2011

nth'ing swapping the monitors. Normally when you see a static residual image on a monitor that can be cleared by windows, its a "write delay" or memory issue.
posted by samsara at 6:24 AM on January 3, 2011

You haven't done anything funny with the cables recently, like make one of them 35 feet long, have you? I get something vaguely similar when I use a DVI cable that's too long. When I use an active extender, it goes away.

Could also just be a bad (short) cable, or interference from an outside source near the cable. It's possible you only notice it on text because it's higher contrast than most images.
posted by supercres at 7:57 AM on January 3, 2011

Booting with the install DVD and switching monitors make sense. Make sure you set the resolution to exactly the same when running off the install DVD. It sounds like a memory issue- if the resolution isn't the same, it won't be using the same "spots" in the memory and you won't actually be testing anything.

But what confuses me is that the two symptoms don't exactly line up. If it was bad video memory, the corruption would be always on the same pixels- moving the windows would have no effect, because the video memory is a bitmap, leading me to think it is something else. But the fact that the corruption only happens in certain areas brings me back around.

(Does OSX use the 3D mode of the GPU like Vista and 7? Maybe that would explain it- the video memory is bad, and part of the screen bitmap is stored on the bad spot. But also some of the windows are stored in the bad spot as 3D "shapes"?)

(Maybe there are two things happening at once. A monitor can have a funny spot that you wouldn't notice unless a certain pattern was displayed, and

Wait, never mind. It is probably a bad spot on the monitor, that manifests as horizontal ghosting. Remember the old, old laptop displays that had this ghosting effect? There would be a streak anywhere there was greater than a certain percentage of "on" pixels. Newer LCD panels can fail this way. Almost for sure this is it. Not the video adapter.
posted by gjc at 8:28 AM on January 3, 2011

You haven't done anything funny with the cables recently, like make one of them 35 feet long, have you? I get something vaguely similar when I use a DVI cable that's too long. When I use an active extender, it goes away.

My monitor does a similar thing if the power and ethernet cables are laying across my VGA cable. If it's not that, test the video card.
posted by thsmchnekllsfascists at 8:49 AM on January 3, 2011

Apple replaced the video card and it was better.

Huh. Mine used to do that in my old apartment, but it cleared up when I wiped the drive and installed from a clean slate. I'd also get really weird static patterns that would replace all the icons for 5-10 minutes at a time. Weirdest thing I've ever seen on a mac.
posted by thsmchnekllsfascists at 7:31 AM on January 4, 2011

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