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Die 2013er Neuauflage des Mac Desktops, bekannt als Mac Pro.

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2013 Mac Pro runs much slower than normal and fan runs at full speed

Does anyone have a suggestion as to what could be causing this? I have zapped the pram but the trash can will shut down after the 2nd startup tone. I have removed all the ram and reseated them, had a brief problem with the ram stick not showing up in slot 1 verified by System Report.

I have left it unplugged from power for 12 hours (while sleeping) and then held down the power on button for 10 secs. That did not seem to affect the bad behavior at all. Fan still at full speed.

Ran the Apple Hardware Test which is built in, and it reported there may be an issue with the SMC Power Manager. I just ran it again and it comes up with the same error message: There may be an issue with the System Management Controller (SMC) Ref. Code PFM006

HELP, I don’t know what to do now.

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I know you said you reset the PRAM but did you do an SMC reset already too?


Same here after CPU upgrade. Damaged GPU?


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See SMC Problem Reference Code PFM 006. They go over the same error code but with another Mac. It looks like either its moisture-related, or virus related. To be safe, follow the instructions by DanJ on the thread I linked above, and then once you reinstall the OS, try to run Apple Hardware Test again. If you get the same error, it’s probably hardware related.

Let me know if this helps!


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I have a 2013 MacPro that had the runaway fan problem noted by others. It had been upgraded to a 12-Core 64Gb machine with a 1Tb SSD and an external Thunderbolt-connected 10Tb MaCie Big2 RAID drive, and had been running happily in that configuration for months, until the fan started running at full speed.

Typically it would run OK for anywhere from 5 to 20 minutes before the fan would flare up to impressively full speed, with the machine still stone cold, and no sign of overheating anywhere, and performance totally choked. This happened with pretty much any application running, and once with none.

I tried re-setting the SMC, VRAM and PRAM, all to no avail. I re-installed Big Sur (don’t get me started on the issues I had with that!)

A look at the Activity Monitor revealed that the culprit was somewhere within the kernel library. Processor utilisation was up over 85% and the only sign of abnormal activity was the kernel library. I re-booted in Safe Mode (restart holding down the Shift key) and used Terminal to get access to the kernel library (just type “kextstat).

The full list of kernels ran to more than 155 lines on my machine, but the Apple kernels are all named “com.apple.something,” so I started looking for rogue kernels that might trigger the problem. Some of them can just be removed, others will need the removal of the corresponding application to remove them. I didn’t lose anything that mattered, and I noticed some of those apps predated Big Sur and wondered if they were 32-bit apps causing issues.

Restart … and a few minutes later, the fan was running hard again.

Virtually the only slightly unknown application left in the application folder was a LaCie disk management application that I used to set up my Big2 drive in Raid 1. I un-installed the app, the disk works fine, and kernel activity is down to around 3%. After more than 24 hours’ continuous running, no sign of any further flares from the fan.

It’s hard to say that the LaCie app itself is the culprit, but it seems that it was interacting with something that was a problem. So far so good — I hope that helps.

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I have the exact same problem, same model trash can. Trying to zap the PRAM, it will do one chime but then shuts down. Plus it’s running very slow. I erased the internal SSD and now trying to install Big Sur.

What the heck is going on here?

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Did you guys ever get a solution. I have had the same problem for 2 months. I have also found that for some reason mine seems to be temperature related which is either something to do with maybe the fans cooling the air and creating slight moisture. If I keep the Mac running at above 35 degrees C it will reboot OK. However if it drops below 29 degrees C it just won’t boot at all until I use a Hair Dryer to warm it up a little.

Very strange that many people are getting this problem.

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This sounds like a power supply issue, time to visit someone who repairs mac's or go directly to Apple.


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PRAM and SMC do different things, both should be reset.

look up how to reset the SMC circuit using a wired apple keyboard for your year Mac Pro.

I couldn’t read the text on the diag report, blurry.

I’d very carefully gently reseat the memory and pay attention to which slots you have them in.

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Run your Activity Monitor. I’ve had the same issue and it turned out to be a single executable, called “kernel_task”which was running away with itself (1,934.6% of CPU), and which I deleted, and the problem was solved, and hasn’t returned. Since then I’ve upgraded my SSD, RAM and CPU — and it’s all still running fine.

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They didn't fix things only hide the issue!

What you are seeing is a special file SMC uses to reduce the CPU's clocking to prevent your system from burning out the CPU chip ($$)

Thats like disconnecting your cars brake cable as your brakes squeal! Just not a good idea.

While not very detailed here's what th diagnostic errors mean: Apple Diagnostics reference codes

If you get any of these you clearly have a problem which needs investigating.


That's about the dumbest thing I've seen today. There is/was no Apple error code associated with the condition. That "kernel_task" in the activity monitor doesn't have anything to do with CPU temp, brake cables or squealing. It's a manifold reference for the operation of unspecified kernels, of which the average Mac has hundreds. I should have been more specific, as I was in a previous post. I disabled a specific kernel in the kernel registry, which was one of only a handful of non-Apple kernels, and which was associated with a LaCie RAID array I have connected, and the problem disappeared. The "kernel_task" activity registers all kernel activity, and is consuming about 2-2.5% of CPU at any time — UNLESS there's a specific task underway, in which case it spikes briefly, or there's a kernel in some kind of recursive loop, which is what happened to my machine. Software de-installed, kernel removed, and the RAID array is fine, no issues with PFA or any other functions. The CPU is running well within it's envelope.


A more detailed description of how to manage kernels is in the bottom of this article. It's not that hard but it's not going to happen in 1024 characters. Follow the link: https://www.makeuseof.com/tag/fix-mac-ke...


@bigkiwiboy - Ha! You fell for it. Sorry TheMakeUseOf link is somewhat wrong!

Let's think this through your system has a System Management Controller (SMC) which does all of the housecleaning task. In the MacPro it manages the fans and monitors thermal & voltage sensors throughout your system.

SMC talks to the OS as one of the OS processes kernel_task. When your systems SMC senses a deadly event high temp or a fan failure or if one of its thermal sensors fails to respond it will alter the process to create empty processes to chew CPU threads reducing the CPU's ability to process. So when you delete the process you loose the ability of SMC to communicate. If you just kill the process then when you restart the kernel_task process will reappear. If it doesn't then you deleted it!

"Still Have High CPU Usage? What to Do When All Else Fails

The final solution here is a bit of a risky one: removing Apple's own kernel extensions. Doing this is not recommended. However, if you've tried everything else and are still seeing kernel_task causing high CPU usage, this is a solution you may want to try."

But, you failed to fix the root issue you only reset things if its still present.


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macisgr8 wird auf ewig dankbar sein.

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