|Sep 21, 2005, 11:02 PM||#1|
Graphics Card Wierdness (G4 MDD)
Thought I'd post this in case anyone knows what's causing it. It's kind of a long description, but a strange problem.
A few days ago I turned on my machine and found strange noise overlaying the display. Opening new windows and movind them around only increased the ammount of noise present. After rebooting the nosie got even worse, and there were several vertical stripes of perpetually screwed up pixels spaced evenly across my monitors.
My machine is a Dual 1.4Ghz G4 with a Radeon 9700 graphics card. I am using two displays. One is an Apple flat panel with an ADC connection, and the other is an old Studio Display that uses VGA. Both monitors experienced nearly identical patterns of noise.
My first though was that the graphics card was dying or had become loose.
I removed it, checked that it's fan worked, removed any dust I could, and re-inserted it. This helped the problem, but did not eliminate it. After checking aroung online I foudn a few posts about this problem that all ended with the poster replacing the card. I was about to bite the bullet and try to find a repair place that could replace the card when the real wierdness started.
I was backing up some files to an external drive when suddenly newly created windows were free of nosie. I playe aroudn and found that anything the machine re-drew at that point was fine. If I logged out and back in, the noise was completely gone. It would only return after sleep or shut-down.
I did a little trial and error and found that the appearance of the noise seems to be realted the the temperature of my CPU. As the chips warm up from room temp, the problem gets better. At 57 degrees C there is a major improvvement, and the noise is gone by the time it reaches 58.2 degrees. Also of interest is that the large case fan next to the Graphics card and CPU increases in speed at 57 degrees. This fan sees totally controlled by the CPU temp. I've watched this happen several times and it seems quite consistent. The noise will not return while the CPU is at it's normal 58.2 degree temperature.
I am wondering if the card is really the problem (as the posts I found indicated), or if there could be some sort of odd cooling issue. Could the card be overheating until the CPU warms up and activates the fan. I have found that running either the quick or extended apple hardware tests while the noise is visable will result in the card failing. If I run the tests after the processor has warmed up and the noise is gone, the card will pass every time.
I'm probably going to take this to a repair place next week, but I'd be interested to hear if anyone has had a similar problem or has a theory on what's happening. I'd love to solve the problem without having to replace the card since 9700's (and anythign else with ADC for a g4) seem hard to come by.
|Sep 22, 2005, 05:35 PM||#3|
It does sound like an overheating issue to me. It makes sense that as your CPU temp rises, and the fan spins faster, that a side effect would be that the graphic card will cool off a bit. I also have a MDD (dual 1.25), though with a Radeon 9800.
One quick way to check is to under-clock your video card for a bit. Try installing ATIccelerator (http://macupdate.com/info.php/id/15849) and then open up the pref panel and lower your Video Card's processor and/or memory speed a bit. See if this clears up your problem. If it does, you can keep it at that lower speed (which will degrade your performance a little in games and 3d programs).
You could also buy a third party heatsink (with or without fan attached) and replace the video card's existing one. Then you can probably run the card at full speed (or more). Both of those options are cheaper than getting a new card if you'd rather not spend too much money. Underclocking your card won't harm it at all, but be careful not to overclock too much or it will fry.
|Sep 22, 2005, 05:48 PM||#4|
I wouldn't bother trying to under or over clock anything, or replace any heat sinks on the video card. It sounds like the thing is toast, and Apple Hardware Test confirms that. It's time for an upgrade.
|Sep 23, 2005, 12:24 AM||#5|
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