iMac Freezing

I have an iMac (white) 17" and have recently been experiencing this freezing issue. It usually happens whenever I am in full screen mode in any application. I don't know if anyone else has reported this, but you can "fix" the frozen screen by simply performing a command+tab. This has worked every time for me. I have not had to power down once. This of course proves the problem is some kind of graphics card redraw problem right? The freezing has become more and more frequent now though and this "fix" is becoming a very annoying problem. Is there anything a 17" iMac user can do besides buying a new computer?

OK, today I installed my new 7600 graphics card. It took me 3 (yep 3) tries to get it to work, the connection wasn't clean and caused my iMac to not recognize the card. I can't post pics because photobucket is down for maintenance, but anyways...

I installed a new (uhm... not really new, it's obvious to me that the cards they ship from welovemacs.com are used cards harvested from imacs they've bought) and a new 500 gig hard drive, since I was in the case anyways. I also took the radical step of drilling a bunch of ventilation holes in the back of my iMac (24" late 2006, 3 gigs memory). I drilled 6 holes right over the fan housing that feeds (directly) into the cooling brick for the graphics card. I also drilled maybe 20 holes where the cooling brick for the graphics card sits. So my iMac is now thoroughly ventilated, for better or worse.

There was a lot of dust inside, but not as bad as I expected. I cleared it all out with a combination of canned air and a shop vac. The local kids were thoroughly entertained to see the inside of my computer in such detail.

This job is time consuming but NOT hard so long as you're familiar with opening up delicate electronic equipment and you have the tools for it. If you don't know what a "torx wrench" is then maybe you don't want to do this.

Anyways, everything is now running nicely. GPU temp is hovering around 40c, so we'll see if this makes even the slightest difference in the long run. I have everything turned 'on' including Quartz Extreme, the one thing that made a 100% difference. When I turned QE off all my problems stopped, as soon as I turned it back on (before replacing the graphics card) I instantly saw the weird horizontal lines on my screen and the computer crashed shortly after.

Updates to come when I have more time and less booze in me 🙂

Edit: Forgot to mention that I haven't yet installed the OS X update to 10.5.8, but I'm doing it right now. So that adds a bit of doubt as to what may or may not have "fixed" my problems, if they updated fan speeds in 10.5.8 then... anyways, too complicated to worry about.

Message was edited by: Micah D.

Wow, has this thread died or am I missing something?

Anyways, since installing a new 7600 graphics card (an upgrade from my previous 7300), upping fan speeds a little with SMC fan control, and drilling about 20 to 30 vent holes in the back of my imac (all done about 48 hours ago) I've had zero issues with freezes, graphics glitches etc.

I also installed a new 500gb hard drive. The computer seems to be running very well now, fingers crossed.

Micah D., what brand of thermal grease you put? We want photos or videos!! 😉 You can open varios apps at the same time? (dvd player, google earth, render, etc...) No more horizontal lines? ok, ok... finger crossed too.

But the cuestion is why Nvidia card fault? I think is bad material but is not Nvidia officially recognise. Is posible Nvidia bad bump material ?

Sorry, no video or pics, I have limited time and had to spend it fixing not photographing 🙂 The links and previous instructions in this thread made it easy, but do NOT start on this without several hours of time to work on it, all the right tools (including several sizes of Torx wrenches from 5 to 9) and printed instructions of what to do. It also helps to have a working understanding of electronic devices and how to take them apart and, of course, the nutz to do something that could very well result in a $2k+ paperweight.

After the first time through, though, if you're fairly competent you can do it all again in about 15 minutes instead of an hour or more. I know. I had to dismantle my entire iMac (twice) after installing the new graphics card, once because the connection wasn't good so I had to clean the connectors, and a second time because I... uh... forgot to plug in a wire from the card to the motherboard after cleaning up the connectors. You'll understand after you do it 🙂

Anyhow, I just ran DVD player (Spongebob Squarepants the movie), Google earth (panned and zooming around), a youtube video on HD and a video via itunes all simultaneously with zero problems. A month ago I couldn't even watch a video in full screen mode without the entire system simply freezing up.

My set up now is: Late '06 iMac with 3 gigs RAM, 500gb HD (new, no relation to the problems I just wanted a bigger HD), new Nvidia 7600gt graphics card, SMC fan control running CPU fan at minimum 1800rpm, HD fan speed min 1600, DVD fan speed min 1500 and about 25 or 30 vent holes drilled through the back of the iMac's case for better cooling.

GPU heat is hovering at 40c at all times.

So far so good, knock on wood 🙂

All seems well now. But it's only been two days, so we'll see

Ahhhh... the final test: The Office on Hulu, HD, full screen. This was the start of me realizing something was really wrong. Every time I'd watch anything on Hulu, HD, full screen the whole system would freeze solid.

Now... no problem. Video comes up clean and clear, and with much less lag than back before everything started going south, thanks to upgrading to the 7600 card I assume.

Now if it would just last.......

"GPU heat is hovering at 40c at all times."

The only way to test that what you did is working is to let the fan speeds run at their normal rate without SMC. I don't have any problems either when my system is around 40 C and I didn't change out a GPU.

So turn-off fan control and cover those holes up and see if it crashes. If it does then issue is the logic board and not the GPU. Then we will have evidence that the problem is not GPU dependent and that we probably all have the same problem.

Zachnap wrote:
"GPU heat is hovering at 40c at all times."
I don't have any problems either when my system is around 40 C and I didn't change out a GPU.

That's nice for you, but I was having problems at all temps and times until I did two things: Turned off Quartz Extreme and increased fan speeds. After that, no problems at any temperature. I don't think upping the fan speeds did anything really, I think that by then it was too late: The graphics card was fritzed from being too hot for too long. Disabling QE just relieved stress off the GPU and allowed things to limp along.

So turn-off fan control and cover those holes up and see if it crashes. If it does then issue is the logic board and not the GPU. Then we will have evidence that the problem is not GPU dependent and that we probably all have the same problem.

No thanks. I'm not offering up my computer as a guinea pig for this thread. I only care about results, and the result of a new graphics card is my computer no longer acts all wonky. The increased fan speeds and venting are simply to hopefully prevent this card from overheating and borking like the last one.

If it starts crashing and acting weird again any time soon then I'll assume the mother board is, in fact, the final problem and probably buy a new computer.

But... let's do some logical dissection here... My iMac was crashing at any/all temps whenever I did anything involving serious graphics use (while QE was enabled anyways). Since temperature wasn't relevant to when my iMac crashed, it can safely be assumed it crashed at 40c at one time or another.

Since the computer is still running at 40c and there's now zero crashes doesn't that rule out the idea that it's the motherboard? If it were, my computer would still be crashing since I did nothing to the motherboard and it was previously crashing at all temps, including the one it's running at right now.

I still think it's exactly what most of us have believed all along: The ambient temp inside the computer got too high for too long and _the graphics card_ got fried, producing unpredictable weirdness for many people. Replacing the graphics card fixes the immediate issues, and increasing venting and fan speeds will (fingers crossed) prevent the new card from over heating and frying like the last one.

One other thing IMO supports this idea: The graphics card has MASSIVE heat distributing features built into it, meaning that obviously the graphics card needs to be running cool. The motherboard, OTOH, has virtually no heat distributing features built in (that I could see) indicating to my mind that it's not very temperature critical, at least not nearly as much as the graphics card.

That graphics card demands lower temps than these iMacs provide IMO.

Only time will tell, though. See you in two years, right? 🙂

Yikes..video card is a bit pricey from that place. Micah, please keep us posted on your success.

With SMC on default/off I've noticed fan speeds much higher than before the recent os x update. I'll try that and see what happens. this thing freezes All the time. I'm happy to be able to finish writing this reply without a freeze.

I think ours cards have Nvidia bad bump material,

Interesting: http://www.theinquirer.net/inquirer/news/1049921/inquirer-confirms-apple-macbook -pros-nvidia-bad-bump-material

"I still think it's exactly what most of us have believed all along: The ambient temp inside the computer got too high for too long and the graphics card got fried, producing unpredictable weirdness for many people. Replacing the graphics card fixes the immediate issues, and increasing venting and fan speeds will (fingers crossed) prevent the new card from over heating and frying like the last one."

I actually remember a period of time when I was thinking: "Why isn't my fan ever running?" It didn't run for months - maybe 6. I wonder if there was a bad update which shutdown the fans for a period and the damage was done then. Then it was updated and fans started working again and Apple just was silent about a bad software update.

Information exposed seems up to now the most plausible cause for the symptoms we experience. This has to be addressed by Apple. Replacing the gpu with identical or new second-hand graphics card with the same lead solder will not solve the problem.

Same issues here - on both my 24" iMac (Nvidia 7300) and on my wife's 20" iMac (ATI1600) - both on 10.5.7. Fan Control has helped things limp along for a few months but now both computers disclose frequent beach balls and lines. Over 124F (51C) on the GPU (using iStat) and the lines appear and lock-ups start. I have turned off Quartz Extreme in both. Today the 24" showed lines (using Lightroom) at 119F (48C) so matters seem to be getting worse.

I'm gutting the 20" today (using the Apple repair manual cited earlier) and sending the logic board for repair to http://www.apples-r-us.net/ - their site says $195-$249. When dismantled I will adopt Micah's approach and drill holes in the rear case to enhance air flow. I spoke with the vendor and they stated they use upgraded components to replace fried ones.

I will probably upgrade/replace the GPU in the 24" with a new Nvidia 7600 from http://www.applepalace.com for $231. Their site states the board is new.

Message was edited by: Thomaspin

I am going to have my 7600GT replaced with a new one this week. My iMac is still unter AppleCare Coverage, so it is not going to cost me. If it helps, I am going to post it here. At the moment it is NVChannel all over the place.

I'd love to hear how the 20" board repair goes. I could actually justify a $200 repair. The logic board replacement is just too expensive for a unit that's nearly 3 years old.