My Mac Pro spontaneously restarts

Thanks for the update.

RAM appears to be my issue too, works with Kingston in it, but starts shutting down with Crucial RAM installed.

Out of interest, how are you cleaning the contacts? Do you mean just with compressed air or are you using something else?

Thanks in advance!

Those RAM modules use "wiping contacts", so just the act of removing and re-inserting cleans them a bit. You can also use contact cleaner. This mostly just removes corrosion as a distraction -- corrosion is not usually THE problem.

The Mac Pro uses Error correcting Code (ECC) memory. Additional check bits are stored with each write and checked by Hardware in the XEON Processor on every read. Single bit errors are corrected on the fly, and are noted in:

About this Mac > ( More Info ) > Memory ... as a status other than "OK". (In some cases, they may turn on the red lights adjacent to the modules on the riser.)

Uncorrectable double-bit errors cause a kernel panic that is distinctive in that it is a "Machine check" and "Uncorrected error" will be listed in the description. Sometimes these panic logs are abbreviated because the error happens in the error handler.

OK - back to the early 2008 Mac Pro restarts:

I 'solved' this issue about a year ago by vacuuming out the dust and removing and re-seating the RAM cards. It was good while it lasted..

However, for a few weeks now the Mac either hangs on the 'spinny wheel' and fails to start, or crashes after 5-10 minutes of operation, usually with funny coloured lines all over the screen.

Research suggests it could be the graphics card failing. Looks like replacement 8800 can be had on ebay...any suggesttions???

Hi,

My problem turned out to be a faulty RAM riser.

I moved the 'big' RAM to the bottom riser and took out the faulty one, no issues since (though I've already bought a new Mac as it took so long to solve).

A new riser should arrive tomorrow, hopefully all will still be well.

Riser is cheaper than a new graphics card or new RAM, so it's worth testing it out!

Look guys, I don't want to be rude or anything, and I think that several different things can be the source of this problem, but these 'I removed the dust' stories are nonsense. Get it out of your head.

Dust can't get between a non-moving contact. The only thing that dust can do is build up so it becomes an isolator and parts get warmer. This was a problem with poorly designed desktops from the far past, when they had tiny, weak fans, little airflow and a lot of heat. However, the Mac Pro is has a huge 'warmth draining' / airflow design, if I may put it that way, so it's just about impossible to have it to collect this much dust in a normal environment.

Even if it did somehow get completely plastered on the inside, you'd notice the fans blowing high-speed all the time, since it has a very sensitive temperature-monitoring system that control each fan and all compartments of the case independently.

Seriously, it's like thinking your car drives better, now you painted over the hood.

When you shut off the power for some time to remove the RAM, and plug it in again, some things get reset. That might be just enough to make a difference.

I posted a while back about the restart happening and cleaned everything out and it's been fine since then. The restarts just started happening again. I ran Disk Warrior and Tech tool b/c my extra internal hard drive disappeared from my desktop. Reparing permissions fixed it. One of the fans also made a funny noise. The next day it spontaneously restarted. (coincidence?) I checked iStat widget and the fan speeds were almost the same as the desktop pic I took in '09. So, I again took everything apart and cleaned it all out and, cross your fingers, it seems stable. The bottom RAM module sits face up and had a decent amount of dust on it. Next time I'll clean one riser at a time to see which it is, if that is the culprit. Maybe it's a sign that one of them is going?

It's a great machine and I'd hate to see it go.

(I vacuumed, used a soft, bushy watercolor brush in the delicate areas and only pulled the ram out and reinstered them)

I know what you're saying, Leon, but it works that way and I don't know why. Maybe something is going and that cleaning or reinserting something is changing a contact or something ever so little. No other explanation. Shrugs.

Giggle Cream-

If you want to save money, the Apple-firmware GT120 may be a better choice.

Hi Leon,

Perhaps but ...

I'll put aside the fact that the air circulating through the system can also force dust into unfortunate places and instead suggest that contacts can become contaminated over time and the friction caused by the act of reseating boards and such can clean them enough to make a better contact. It seems to me that unless you live in a hermetically sealed clean room with perfectly modulated air temperature and humidity control, you will have conditions that will affect contacts. Yes these things are engineered to the nth degree, but no matter how good the contact is, the expansion and contraction caused by changing temperatures would be just enough to allow your contacts to become besmirched. So I don't think it is realistic to brush off this "fix" completely. In my case, the cleaning and reseating did the trick when simply working through the reset processes alone did not (and it has been 9 months or so).

Having said that, while I've not had the restart problem since the thorough cleaning, I know in my case it didn't fix the REAL problem. I know I'm having power issues since some of my USB connections that should have power, don't and because I can create boot up problems by using too many of those connections at once. (Note that before the cleaning and reseating it would shut down automagically with empty USB ports ). I also still don't trust the machine enough to set it back to auto restart if it shuts down for fear of it getting caught again in that ugly restart crash restart cycle that I know will do even more harm.

Truth is, I can't afford a new machine at this point and am very wary of shoveling more money into a machine that is already four years old so I'll limp along and clean again and again as long as it works and I don't care if it is pixie dust and unicorns that keep it running just so I can get my work done and keep myself in catfood.

Hi Giggle, When my factory installed vid card went, it did not affect the processor at all. I could access the machine easily from another Mac. In other words, it was running just fine, it just was running blind. As always, your mileage may vary.

Don't get me wrong, I spend a lot of time, way to much time, investigating what was wrong with my Mac Pro. I will not bore you (again) with the details but the weirdest things happend, like RAM that had, accoording to OS X, disappeared, random crashes, etc.

Everything indicated hardware problems. I replaced RAM and power supply, seemed solved more then once, but nothing worked permanently. Finally I realised that I had never done a complete re-install. I wiped the whole disk, did a fresh install / update to 10.7 and ever since, the problems have solved. So try that before you buy something expensive.

Worth trying, Leon. Thx.

Ive upgraded my ram to 6 gigs,on os 10.8.installed presonus firestudio mobile sound card [last week] pulled my rubble of wires out of the way and straightrned up mac pro. no restart problems for months now [thank god] and the intermittent fan noise has gone too...gerry...TT

So for me this restart problem blossmed into a bunch of other problems that finally led to me baking my video card and rescuing my Mac Pro from not starting up at all to being used for 24 hours without incident. I explain what happened and what I did in this thread:
https://discussions.apple.com/thread/4060561

I'll try and remember to post back in a few weeks.

I am not doubting anything you say but after countless power resets and PRAM resets and endless googling with no result I hoovered out the thing and took out and reseated the RAM, end of story and it then worked flawlessly for about a year.

The above is a statement of fact.