So I managed to get my hands on a second iMac for not a lot of money. It's a 2008 model yet with a 3Ghz C2D processor it's quite powerful. Before I bought it I didn't realise that it had the notorious Nvidia 8800GS graphics card with the disastrous flaw in it. It turns out that these GPU's are actually the GTS variants but oddly named with the GS suffix. Due to the poor airflow in the iMac case they slowly break down as a result of heat cycles fucking up the solder. So far this machine has been running flawlessly and after all I've read it may be one of the few surviving. Apparently most of these models have had their GPU replaced several times by Apple only to be scrapped when the subsequent GPU's have failed almost immediately. I'd like to do whatever I can to keep this machine running as long as possible but I'm not sure how to go about it. I'm on my way to the hardware store soon to get a suction cup so I can take it apart and make sure the fans are clean but I want to know if there's anything I else I can do to prolong the life of the GPU. I had a bit of a scare today when the screen flickered black for a few seconds which apparently is an indication that the GPU may be about to give up some time soon. Many have advised more or better thermal paste, others have recommended I force the fans into a higher default RPM but I have no idea what is really going to help. Better cooling may actually make it worse as many users who still have this model have had no problems yet their pattern of use has been to push the system to its graphical limits on a daily basis. Surely if the issue is caused by thermal cycling then better cooling may bring the temp down too low after a heavy load?? I could replace the card with an ATI variant but they're incredibly rare and expensive. Any thoughts? It's such a nice system it'd be a shame to let it die but then it's a bit too old to spend any serious money on either.
You might be able to find a person that could reflow and reball your GPU for you. Unfortunately, that would require finding a local shop but if done right it's a repair that's very worthwhile. From there, you might want to redesign the cooling system in some way. Whether it's through adding additional or more powerful fans or possibly changing air flow, anything of this sort would be very helpful. Doing all of the above would be like a permanent fix for this problem and it should actually be pretty inexpensive provided you can find a good reballer. Otherwise, you can go with the idea of finding a replacement card. Look into everything that the board supports, and wait a little bit until you can find an unusually good deal on it. Good luck!
The problem isn't restricted to specific NVidia chips, it affects even their desktop cards. It's the cooling that seems to determine whether it will fail or not. It mostly affected laptops because for power/sound issues they let the chip get really hot before trying to cool it down again quickly.
It's not the solder under the GPU chip that is the problem. It's the internal balls on the flipchip that break. The fail is caused by the sealant (underfill) they used to keep the die on place not being resistant enough. Then the flipchip balls inside the package break, causing the GPU to fail. http://www.empf.org/empfasis/2010/Apr10/flipchip.html Reballing it will at most "freshen" the balls inside the underfill which could cause it to achieve a few extra hours of operation. :topsy_turvy: Same reason why XBOX360s and PS3s fail and the chips sometimes cannot be re-used or fail again shortly after re-ball.
So it looks like failure is inevitable :-( Well there have been very few reported failure's with the ATI alternative. It's £219 for the part but may be worth it just to keep the machine going. I don't have the heart to sell it on, I'd hate to have someone knock on my door looking angry in a months time and then have to lie saying I knew nothing about it.
That's a trait a lot of dealers and sellers have been missing of late. If everyone were concerned like you and thought of the others, the world would be a much better place. I for example have this repaired PS3 I would love to sell out but I am fairly sure it will fail again so I just can't sell it. I am using it to play instead of my own PS3... lol
I've got some hardware like that too. Had two IDE Maxtor drives of considerable size when they were starting to fail inside their respective machines. *CLICK* and Windows would freeze. One went into an XBox and the other into a PS2 where they kept on humming along for at least 3 years when I sold them both. Last I heard they were still running like a champ. Bloody damn things.
Well I've been using the machine for Dev for the past two days straight, I've been streaming HD video on it a lot too. It's never missed a beat. The only weird thing is that it occasionally hangs when playing a track in iTunes (please don't bombard me with iTunes hatred). Everything becomes unresponsive until the track starts playing again (though the mouse is still operational so it's not a total freeze). Not sure what could cause that. Hard drive checks out ok and I zero-ed it before installing OS X.
Like you said, the MxM graphics cards are really expensive, despite being cheap models. You could by a modern gen MxM for the cost of an Apple one, with the only reason being it's an Apple card. Flashing is no good either because even if you found an MxM laptop to flash it with, it needs an extra large BIOS chip to handle Apple's EFI boot. So, you can't fix the card, but I could suggest that you use a fan controller of increase the GPU fan speed. Keep in mind sometimes the fan controller doesn't have a GPU fan speed but will have an ODD (optical) fan- this is for the GPU. Or, at least that was the case on my old iMac, and a lot of them, before the 2012 redesign had similar placement of internal components and heat sinks in the same display size. Always check for some person selling an iMac with a dead logic board or a cracked screen on any local listing site- if you know how to do the removal well you can see if they'll agree to let you remove the part you need, and if they don't know it's worth, chances are you can sneak it off for a cool $50. If the person doesn't know much about computers blabber on about how the screen panel and motherboard are the most expensive parts of the computer, not the part you need. Oh right- CLEAN IT OUT. Those damn nice cases trap so much dust. My iMac dropped 10C after a lightly cleaned out the heatsinks. I'm going to assume it's a 24"- Use ifixit.com as a site to have step by step instructions on how to open that sucker up. Soon as the glass and LCD are removed, access to the rest is a breeze. Compressed air, and put it back together and that's a nice, quick fix.
Thanks for a few tips. I've already had it open and it was incredibly clean inside, either it's not been used much or someone has been in before (hopefully Apple to do a gfx card replacement). Yeah I read plenty about the MxM cards, it's mad how you're so limited between upgrades due to EFI version and MxM version but then I guess Apple doesn't want anyone upgrading without buying a whole new machine. It is a 24, I'm thinking the best route for this machine is to carry on using it until the GPU dies and then find another 24" (preferably 2009) with a fucked screen and use this as a donor. As for the iTunes issue, it doesn't happen if I'm continually using the machine, but if I just leave it playing music while I do other things then it regularly freezes. I have a feeling it's the harddrive as streaming netflix for 3 hours without interacting with it caused no freezes at all so it must be something to do with data access. Running a time machine backup can also cause a few problems.
