Crazy Pixels

[gphoria]

Howdy everybody,
I just bought a used TiBook(1ghz g4) to replace a TiBook with a failed L2 Cache and I'm having some difficulties with it and I'm not sure what the cause is. I've been using macs for 12 years, powerbooks since pismo and I've never seen this so maybe I've just been real lucky.

Basically when it starts up everything looks fine but then sometimes for no reason when I start opening files or browser windows the pixels start going crazy getting stuck in dying out. Sometimes when I restart it works fine for hours and sometimes I can restart five times and it happens ever time. I just reinstalled OSX Tiger and it didn't help as expected. I don't know how well I explained this but hopefully someone understands. Is it possible that I have a loose video connection or something stoopid like that?

Any Help Is Appreciated,
Tim

 

[Makosuke]

A loose video connection can cause problems like that, although I wouldn't expect a restart to help were that the case.

I've had a somewhat similar problem with scrambled graphics that was due to a bad graphics card (desktop in my case); that MIGHT be affected by restarts, although again you'd think it wouldn't. Does it do it when you're booted from a DVD? If not (as in, definitely not), then that points to either some weird software problem (though one that isn't fixed by a clean install seems odd), or that it's the graphics card--a "proper" OS install does less graphical acceleration than the install DVD, which is what happened in my case.

If it is the same when booted from a hardware test disc or an OSX install DVD, then it's probably a bad connection or bum chip (overheating, maybe?).

 

[gphoria]

Thank You for the reply. I will monitor the situation and try to reply. So far, as far as I can tell, it's been intermittent. I've been trying to make it fail and have had little success. It just happens when it wants to I suppose.

 

[gphoria]

I'm guessing I'd have to remove the screws from the bottom to get to the video connection, yes? I've been into my other Powerbook at least a dozen times in the past two weeks but when I lifted the keyboard last night on this newer powerbook it was instantly clear that they are very different (TiBook G4 400mhz vs TiBook G4 1ghz).

 

[gphoria]

OK. I was playing Full Tilt Poker for a few minutes and after about twenty minutes the screen started with it's usual antics of "mass pixel failure". I put it to sleep for a few seconds and when I started it back up the were a few "stuck?" pixels but they went away. I proceeded to play for a few more minutes and then they were back to their old tricks. I put to sleep again for about a minute and now it's fine. I'm confused.

 

[gphoria]

I'll just keep posting things as they happen. I found someone else with the same problem on a World of Warcraft forum but unfortunately it's subscription based and I can't contact the person but there are photos on the forum here:

http://forums.worldofwarcraft.com/t...777919C659C417D4D4D2BA?topicId=86715001&sid=1

Ironically, it was happening as I was reading the post. I don't play WoW but I do use Full Tilt and Safari and just like this other unfortunate soul this problem affects both programs on my machine. I noticed that when it happens in Safari that if I move the window, the pixels "underneath" the window become clear and normal which doesn't seem like a hardware issue then to me.

 

[Makosuke]

I noticed that when it happens in Safari that if I move the window, the pixels "underneath" the window become clear and normal which doesn't seem like a hardware issue then to me.

Ok, based on those other forum pictures and the fact that the artifacts follow windows you're moving makes it sound a LOT like an intermittent graphics chip failure (overheating, maybe?).

Thing is, OSX uses the graphics chip to speed up drawing the windows, which is why I wanted to know if it happens in the installer DVD--that DOESN'T use hardware acceleration, so the artifacts won't show up.

If so, this is exactly the same as my problem, and while it could theoretically be software, I assume it's a bum graphics chip.

There are a couple of easy tests you can do:

One, if you take a screenshot and it's the graphics chip, the artifacts should show up in the screenshot as well (which you could post here). This sounds counterintuitive, but apparently OSX takes screenshots by dumping the VRAM directly to an image, so the artifacts WILL carry over if they're being generated in the graphics hardware.

Alternately, you could install the Developer Tools and use the Quartz Debug app to disable Quartz Extreme. This removes the hardware acceleration; if the problem immediately clears up when you do that, it's almost certainly the graphics hardware.

Assuming it is the graphics hadware, bummer--can't replace that in a PowerBook.

 

[gphoria]

I will try the screenshot deal in an hour or two when I can get back in front of it. It did not happen when I had my Tiger Install DVD in but then again it doesn't happen all of the time anywhere.

 

[gphoria]

The artifacts do show up in the screenshot.

Sorry about the file size but I didn't install any graphics apps yet.

 

[Makosuke]

Whelp, since that screenshot looks nearly identical to my problem and it may not show up on the installer, I'd put my money on a bum graphics chip. Not much you can do to fix that, unfortunately.

You might try messing around with stressing the graphics and/or processor to see if it's triggered by heat--if so, there's some chance you could crack it open and maybe reapply thermal paste to the heatsink(s) (who knows, maybe somebody screwed up on a past upgrade) and/or figure out some way to make the graphics chip run a little cooler.

Since it's probably not worth much anyway, I don't suppose opening it up would be a great risk. Only repair method I know of would be replacing the whole motherboard.

I suppose turning off Quartz Extreme might help, but then you're sacrificing any graphical acceleration at all.

 

[gphoria]

It might be heat related , it usually has to be on and out of sleep for a while to happen. But why would putting it to sleep for five seconds fix it? The chip gets no cooler I'm sure. Are there any apps to read off processor temp for OSX? I used to install an XLR8 control panel on all my macs to read temp butit was for OS9.

 

[gphoria]

I downloaded Temperature Monitor but it only shows a temp for the hard drive I think. Shouldn't the CPU have a temp sensor?

 

[gphoria]

I downloaded a temp utility for the doc, looks like it's using the same sensor and reading about 40? C. Seems like normal from what I remember. I had overclocked G3s that ran hotter than that with no problems.

 

[Makosuke]

I don't think the G4 in that model has a temperature sensor that can be read, although I suppose you could try this app if you haven't already:

http://www.kezer.net/shareware/thermographx/index.html

40C is downright chilly for a processor (G4s can comfortably run at at least 60C as far as I know, and probably quite a bit higher), and about normal (I guess--they can get hotter, certainly) for a drive, which like you said is probably where you're getting the reading from.

Even if you were getting a temp reading, it would be for the processor, not the graphics chip anyway. A better idea would be to just put the 'Book on something very heat conductive and relatively cool (ideally, one of those laptop trays with industrial-strength fans, or use it on a tableoutside when it's cold) and see if it helps. If so, probably heat related. If not, it's just busted.

And again, even if it is heat related, there's not much you can do--poking around inside is your best bet regardless.

 

[gphoria]

It hasn't done it at all today. If it was heat related is there any fix? Replacing a fan or anything? I always put my Powerbooks on a Roadtools Coolpad that gives it good airflow underneath.