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Joined: 13 Dec 2016, 22:46

Mac Pro - what determines fan speeds?

13 Dec 2016, 22:51

I've got a Mac Pro (early 2009) that I upgraded with an Intel Xeon W3690 (3.46 GHz) a couple years ago. Of course it has the MacPro5,1 firmware as well. It's been absolutely rock solid, but ever since upgrading to Sierra, the fans quickly go out of control for no apparent reason. Temps are more than reasonable, ranging from around 71°F ambient and DIMM temps to a max of 96°F at the power supply. CPU temp (heat sink, diode) is around 85°F (CPU core is about 75°F). The PCI and PS fans are fine, but the exhaust, intake and Boost A fans are running at full speed non-stop. I'm attaching a screenshot that shows the fan speeds and temps, and you can see that exhaust, intake and Boost A are maxed out when left to their own devices:

Screen Shot 2016-12-13 at 4.38.33 PM.png
Screen Shot 2016-12-13 at 4.38.33 PM.png (137.6 KiB) Viewed 2772 times

I have thoroughly cleaned the case and fans of any dust and debris. I have repeatedly reset the SMC. On restart the fans are fine, but then for no reason those three will eventually jump to full speed again even when temps are fine and there's no load, and they don't slow down unless forced (e.g. with Macs Fan Control) or the computer is rebooted (lather, rinse, repeat). Computer has all of the latest OS updates, and no processes are running amok.

Any thoughts? Again, this only happened after the Sierra update. I searched but haven't found similar reports, and I can't imagine Apple is going to be too helpful with a 2009 Frankenstein machine (unless I wanted to pay through the nose for support). Obviously I can force the lower fan speeds with Macs Fan Control, but I'd rather solve the problem. I guess I'm wondering what specifically tells the computer to make these fans go faster.

Barring a real fix, suggestions on temp ranges (especially max) and which sensor(s) to use to use sensor-based control for the affected fans via Macs Fan Control would be much appreciated.

Thanks in advance,
Posts: 1
Joined: 03 Feb 2017, 08:26

Re: Mac Pro - what determines fan speeds?

03 Feb 2017, 08:37

Now that is very interesting – I'm on nMP (trashcan one) 6-core/D700 and have eerily similar problem.

Box ran flawlessly since 2014 until I've upgraded to Sierra – since then system fan goes to jet engine mode just after the boot. As I type this, it goes full blast standing under open window, temp readings 18º-40º C in all sensors, 2% CPU load. And it seems to throttle CPU, stuff became definitely slower.

SMC reset, NVRAM reset did nothing. I even took it to Apple service, where they've ran diagnostics that showed all green and two error codes which I've seen in Apple Diags: PFM006 ("SMC made a boo-boo") and PPN001 ("unknown error with power subsystem, which Apple Support have no idea about (!)").

At the service though box DID NOT do high fan speed, and remained normal for a couple of days. Service tech said it was an SMC error due to some of the peripherals (which worked flawlessly for 2 years BTW - USB mouse/kbd/sound, TB display, nothing fancy at all).

I tend to blame Sierra sneaking buggy SMC firmware update or something like that.

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