Q: My Mac Pro spontaneously restarts

TIM stands for Thermal Interface Material.

In most cases it is a paste of some description with high thermal conductivity, but there are some more exotic ones, including the one that Apple used at least in the Mac Pro that I have. It looks and behaves like liquid metal.

It is used to "bridge" the gap between the processor's heat exchanger (top surface) and the heatsink.

If TIM loses its heat conducting properties or surface contact quality (for example due to its old age), CPU can't transfer its heat fast enough to the heatsink, and thus overheats, which may lead to system reset by the SMC (that's what I'm hoping).

so it's been at tekserve for 11 days now. They swapped logic boards no go...apparently they're on the phone with apple engineers?! They say another one's in with the same problems and no luck with that either....

Very interesting. This is exactly why I rather wait for a Mac Pro update and buy a new one then throw more money at a new motherboard. Over here (Netherlands), there is no repair company that offers 'no cure no pay' motherboards… :·\

Yeah this *****. Tekserve is pretty good. I'm friends with a few techs there and for the machine to be still be in the shop after 11 days for anything besides data recovery is basically unheard of. Whatever's going on it's unfortunate that Apple's keeping mum- this isn't a bad run of some part, it's something bigger.

I reported earlier I thought it might be an external firewire HD because the computer restarted when I plugged it in.  However that was short lived.  Recently I blew it out with a compressor and removed and reset the RAM. That was over a week ago and no restarts so far.  After talking with a local tech guy I don't think it is a one problem fixs all situations reported here.. so not actually Apple keeping mum.  It's just a that there are several things that are known to trigger this restarting issue. 

Ok, I have identified the problem with my particular computer (please see my post on the previous page which details all I tried before this).

So, today I got my thermal paste and replaced the original one between heatsinks and CPUs. To my despair, this didn't help, either.

So I started pulling out memory and putting it back in, one pair at the time (yes, I know - I *should* have done it *before* I started to muck around with power supplies, CPUs and logic boards).

Anyway, I found that what triggers the resetting behavior is a presence of *any type of memory* in Bank 1/2 in Riser B. Original Apple, OWC or Transcend. All trigger rebooting behaviour. It is *not* the riser card itself - I swapped them around. Both work fine when plugged in Riser A slot, with any combination of memory. Both cause machine to reboot when in Riser B slot, with memory in Banks 1/2.

Interestingly, memory in Banks 3/4 in Riser B don't cause rebooting behaviour (but machine doesn' see that memory, as there's "hole" in Banks 1/2), so there's no point of having anything installed in there.

So now I'm down to 8GB of RAM, what with inability to put anything in Riser B, but at least my machine is back, working.

I am really surprised that Apple repairs service guys said replacing logic board didn't solve this. Well, maybe I don't understand it well enough.

Update: computer began restarting again. Not too frequent just yet, but the telltale signs are exactly the same as before. Sigh.

Oh, man. My sympathies. I feel like you've ruled out practically every possibility to a tragicomic degree. Like, have you made sure a family of timber rattlesnakes isn't living in the power supply? Have you made sure your bluetooth coffee maker isn't issuing rogue shutdown commands? One user reports that wrapping the case in tinfoil and placing a quartz pyramid on top solved the problem. Tried that yet?

Mine still hasn't crashed again since I reported a couple weeks ago, but I'm just waiting for it to happen again. On a separate and probably completely unrelated side note, my 2008 vintage iMac at work has starting nose-diving HARD. Just blank white screen and dead. No hint of a kernal panic. Just... dead. Joy abounds.

Dude the Quartz pyramid totally did it. Who knew it was that simple?!

As per my situation. The machine has now been in the shop more than 2 weeks. On the upside because it's taking so long Tekserve threw me a bone and I've got a rental to hold me over until the machine is diagnosed and fixed...I guess there's a chance I'll have this machine for a while then...

Well, that's it, I had it. Went and bought a brand-new 2009 Mac Pro.

And guess what: the new one I got had a hardware fault with its Ethernet board - it would lock up solid in about 5-10 minutes, no matter what it is connected to. Had to swap it for another one (luckily my supplier was kind enough to accomodate this). End of story? Not quite. The one I got now has an occasional monitor flicker issue.

Looks like you just can't win. Wonder what will happen if I write to Tim Cook and calmly explain to him what I am thinking now, after having gone through all of this...?

Anyway, on the issue of the mysterious resets of the original Mac - somebody I know suggested a plausible explanation: in my case Apple said that they replaced the logic board and it didn't fix the issue, as I reported a few posts back. Well, it is well known that they very often use refurbished parts for repairs, so it is entirely possible that the refurbished board they tried in my machine had the same problem as the original one... This aligns with the experience I had trying to buy a brand-new logic board - the supplier just couldn't get one. They waited on Apple for almost two months without any ETA before I gave up and cancelled my order.

Hmmmm...

Apparently you can't have both: either the decent OS X with Apple's vendor hardware lock-in combined with lousy guarantee or Microsoft's Windows with it's annoying behavior and too many flaws but with a choice in hardware vendors with decent guarantees.

For example, I bought a Dell 30 inch screen with my Mac Pro and it came with 3 years on-site guarantee (not that I ever needed it) instead of one year carry-in and has better specs while it was still considerably cheaper than Apple's offer.

In the nineties I thought it was because Apple couldn't afford decent hardware guarantees but now they are one of the richest companies in the world and considering the prices of Mac Pro's, that seems ridiculous.

I found this (LONG) thread while looking for ideas for I think the same basic problem, and I am wondering if any wisdom has emerged from all this discussion.

I too have an Early 2008 Mac Pro (4 core).  In recent times it started rebooting, apparently spontaniously.

The best observation so far seems to be that in the Energy Saver preferences I had "Start up automatically after a power failure" set.  Otherwise I had the defaults.  After I deslected it the machince stopped rebooting spontaniously and the sysmptom was replaced with randommly/spontaniously shutting down.

Looking in the logs there is a lot there, none of which gives any real clue, including why the machine was shutting down.  Various efforts up to and including removing all traces of Adobe AIR, and updating to Mac OS X 10.7.2 have managed to reduce the level of messages in the logs, but none seem to give any clue.

So, at this point I am suspecting mostly a power related issue.  Of course it could be the power in from the wall (no UPS to filter it - but no sign elsewhere in the house, or on that circuit, or on that outlet of any power issue).  But the "usual suspect" list would seem to start with the power supply in the computer.

Any ideas how to test it?  In fact in a Mac Pro tower where is it, and how do you get to it?  And where would you find a replacement - sources? specs??

OK - here's an update on my early 2008 Mac Pro.

Since vacuuming out the dust and removing, cleaning, and then putting back in the two RAM pack board things I have not had a single shutdown or spontaneous restart since.

I think it's about a month now. This was after the problem becoming so acute it was rendering the machine unuseable. It was also doing it in Windows under bootcamp.

I'm convinced this may only be a temporary solution, but, so far, it IS a solution.

Hi

both my older silver doored G4 and now my new Mac Pro have the same problem - restart almost immediately after shutting down - not every time, but often enough to be annoying. I am still running 10.6 OS.

I dont think it is the dust tho as it started very soon after migrating to the new machine. I suspect it is something copied across from the old machine but I dont think it is going to get fixed anytime soon.

Is there anyone from Apple reading this who can offer a sensible suggestion?

This topic started about spontaneously restarting/crashing Mac Pro 2008 models. It's a huge leap to brand new Mac Pro models, since they the inside has been redesigned several times since 2008, let alone a siver doored G4.

I don't mean to be rude, but if every unexplained Pro model problem is posted on this thread, it'll end up being a useless kitchen sink. Already the symptomes mentioned and solutions suggested are shooting in all directions.