Mac Pro 2007 (2,1) fans on siesta

fhturner

macrumors 6502
Original poster
Nov 7, 2007
491
312
Birmingham, AL & Atlanta, GA
Got an interesting one here... Doing some testing on a 2007 Mac Pro 8-core 3.0GHz machine, and its CPU fans seem to regard their charges (the CPUs) with some degree of contempt. When under a sustained, heavy load, the CPU temps will climb and climb, eventually reaching 190F or so and causing the machine to shut off; all the while, the fans couldn't be bothered to budge from idle.

My testing is basically having Final Cut Pro X (v10.3.4) transcode some 4K Phantom 3 Pro footage to ProRes ("optimized" media). During transcode, Activity Monitor shows upwards of 700% CPU usage.

At first, I wondered if this was a product of running the machine beyond its pay grade on 10.11 El Capitan. I thought, perhaps SMC direction is absent for this machine in ElCap. So, I booted to the previous 10.7 Lion disk and retried (w/ FCP 10.0.9 this time). CPU usage appears to peak around 400%, so it takes longer, but temps still climb until the machine shuts off.

I've tried SMC reset w/ the power cord like Apple suggests, as well as resetting using the button on the logic board near the PCIe slots. A quick test using SMC Fan Control to bring the fans up to 2K RPM or so (600RPM is idle, I believe) easily kept the CPUs below 140F and no such shutdowns occurred. While this could work, I'm more interested in *why* it's behaving this way and how to fix it, rather than treating the symptoms.

Any suggestions?

Thx,
Fred
 

flyinmac

macrumors 68040
Sep 2, 2006
3,582
2,408
United States
Personally, I use Mac Fan Control to set the fans on my 2,1 flashed 2006 Mac Pro.

https://www.crystalidea.com/macs-fan-control/download

I like it because it allows me to set the fans to adjust speed based on component temperature.

In your case, I would propose using it to verify that the temperature sensors are in fact working.

This utility essentially provides the same functionality methods that Apple uses to adjust the fan speeds. But allows you to adjust the threshold.

So it might be a good solution for you. As it allows the fans to slow down when full blast is unnecessary.

As for why you're having trouble, I would suspect perhaps something isn't right in your configs or hardware recognition or Kext files regarding your upgrade to El Capitan on the Mac Pro 2,1.

Troubleshooting that area is a little out of my speciality.
 

fhturner

macrumors 6502
Original poster
Nov 7, 2007
491
312
Birmingham, AL & Atlanta, GA
Thanks for the reply and suggestion! I'll give that a look. Regarding the cause, I would've thought the ElCap thing too, but when I tested w/ the supported 10.7 Lion system, it still did it. So I'm thinking SMC somehow. And the temp sensors appear to be working as well, since they show a maniacal march toward 200F before shutdown occurs.
 

flyinmac

macrumors 68040
Sep 2, 2006
3,582
2,408
United States
Thanks for the reply and suggestion! I'll give that a look. Regarding the cause, I would've thought the ElCap thing too, but when I tested w/ the supported 10.7 Lion system, it still did it. So I'm thinking SMC somehow. And the temp sensors appear to be working as well, since they show a maniacal march toward 200F before shutdown occurs.
Good points.

It should work fine with 10.7 and behave normally.

The resetting the SMC and PRAM should be the only things necessary to clear out the hardware issues.

I'd be curious if you reset both the smc and pram and immediately booted into 10.7 how it would behave. Not sure if anything from El Capitan would be sticking in the hardware settings.

The only other thing I could think of at the moment is if the built in thermal control system was glitching or malfunctioning. To where the Mac knows it's getting hot and just isn't able to automatically adjust the fans anymore. But I've never heard of that happening. And at least part of it must be working if it turns off the computer on its own when it gets too hot.