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My computer shut itself off with no warning last night while I was doing backups, and I was actively interacting with it so it's not like it had gone into sleep mode or anything.

It's never done that before.

Can't say for sure it's related to 10.9.3, but more likely some damage done by what is looking to be an increasingly scary update to Safari (see my other thread).

Definitely it is harder to get out of sleep mode when it goes into it, and yet my preference is to avoid sleep mode so it shouldn't be happening anyway. Yet this isn't as scary as the shutdown. I've now had that happen once or twice with each point release of Mavericks after another app is updated to be "compatible" (whether Mail or Safari e.g.).

Yet this isn't as scary as the shutdown. I've now had that happen once or twice with each point release of Mavericks after another app is updated to be "compatible" (whether Mail or Safari e.g.).

Yea, that's not a common issue.

When was the last time you replaced the PRAM battery? There have been a number of reports of that being the culprit. I always carry spares for the Macs I service.

My favorite way to test if that's the issue is to remove it and see if the Mac boots more easily. Most Macs will perform better without the battery than with a weak one. Of course, without one, it won't remember any settings.

First I've heard of the PRAM battery. It doesn't show up in diagnostics or system report. If it can be a problem, I'd think Apple would make it highly visible and part of some tool we use regularly. Is this self-serviceable? Where is it? How does one know if it's bad?

The only thing I've been suspicious of lately is the media drive, as so many CD's load poorly even if tried multiple times, and primarily towards the end if 80 minutes vs. 74 minutes (though I still suspect iTunes, and am rarely able to find any settings that let me force slower disc read speeds). Commercial CD's are the problem, not my own CD-r's of band material etc. I looked at OWC but they only have one brand, LG, and it's black and looks high-profile height-wise and regarding the label, even though OWC says it's compatible with the 2010 MacPros.

I had never had the power down issue until mavericks, but that could be coincidental if the PRAM battery has a shelf life of 3-4 years.

You've never replaced it? Oh my. This is a maintenance item. A good idea is to replace it every three years but it is not uncommon for them to last five or more.

I have no idea what the voltage spec is when it should be replaced nor do I care. You are showing a known symptom. It's not a symptom associated with Mavericks. Replace the battery and see if you still have a problem.

Technically, it's the NVRAM battery but even Apple Support calls it the PRAM, its correct name in a G5.

In the old days, you would find that your settings would not be saved. Beginning with the B&W G3, Macs often stopped booting when the battery was too low - pull it out and you could boot. Apple support boards are full of discussions of erratic behavior and sudden rebooting due to an old PRAM on the Mac Pro. There's even a recent thread on this board.

The Mac Pro uses a common C2032 battery, same as MOTU MIDI boxes, my diabetes meter and Toyota key. You will see it on the mother board. OWC sells it for $1.79. OSH sells Energizer for $3.19 last I checked. I forget what Wallgreens gets for them. I buy them by the 10 pack. Some of the cheap brands do not last as long and it's a real pain to replace them in many items that don't work without a good one. The maker of my diabetes meters insists on DuraCell and will send me one for free if I ask. So I use Energizer or Duracell. Actually, OWC's price is pretty good if you go through them like I do - if one can last three years in a Toyota key, that's as good as anything else.

It's a little tricky to get the old one out on a Mac Pro - don't do it right and you'll break the holder. There's a way to push one edge down and it will pop loose.

Even iMacs have one. Replacing those is a $99 labor charge on my 2010 - higher on a 2012-on unless you are good at suction cups, heat gun and glue. I'm thinking of having an SSD installed in mine - You better believe that, with the glass and screen off, I will have that battery replaced.

The Mac Mini NVRAM battery is easy to reach once you get the cover off with a paint scraper.

They're also in lots of hardware synths and other keyboards, rackmount devices and many other things that retain some sort of memory or preference. When memory starts resetting or a device won't start up that's often the cause. New battery: all is good but you'll have to reload some patches, etc. and reset preferences.

You could also try resetting the SMC and see if that works:http://support.apple.com/kb/HT3964?viewlocale=en_US

rich

Wow, thanks for the info; I just can't believe this never gets talked about anywhere. Maybe most people upgrade so frequently it never comes up. With synths, I'm used to it not being a problem for at least 15 years and usually 25-30 years.

Will I lose a bunch of stuff during the battery transfer process, and is there a way to back something up beforehand to avoid losing a bunch of settings?

Now I'm super-curious about this issue, because someone at work told me my app makes their computer shut down and it's a major crisis that has me working crazy hours trying all sorts of things that are shots in the dark since I can't reproduce their problem. They have a somewhat old computer.