I'm on an iMac 2019 21.5 inches and I want to monitor my computer's temperature. I have the Macs fan control app, but I don't know which sensor to use. There are CPU cores 1 - 4 (sensor reading for each), CPU Proximity, and CPU PECI. I want to make sure my computer isn't heating up when running processor intensive applications. Which sensor should I rely on?


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    Your computer has lots of hardware and software designed to monitor and manage the temperature for you. Unless something is not working properly, and your computer is shutting off to protect itself, it's not something you need to do. – benwiggy May 16 '20 at 8:38
  • This comment from @benwiggy. Why the heightened concern over CPU temps? What are you going to do with this data that the SMC, macOS, and the CPU itself already doesn’t handle? – Allan May 16 '20 at 11:51
  • To be specific, I’m rendering on Blender. – Samarth Kabbur May 17 '20 at 2:06

They're all valid temperature. It's kind of like asking "what temperature is my car's engine?" There's the oil, water, pistons, camshaft, etc. that all have different temperates. Just monitoring the oil temp won't tell you that one of your pistons has overheated.

But here's the thing, your computer won't overheat. Most (if not all) modern CPUs "thermal throttle" when they reach a limit placed by the manufacturer or motherboard. In this case, that'd be around 100°C for most modern Intel CPUs. Thermal throttling means the CPU will run slower, therefore using less power, and thus not heating up as much. It's perfectly fine to run a CPU at it's max temp for years, it's designed to be used and won't "overheat". If you prefer, of course, you could turn the fan up higher (or reduce the workload), but that won't really have any effect on your CPU's lifespan.

To directly answer your question, I have Macs fan control, I usually just set it as the first core, but I've figured out that one of my cores is hotter than the rest, and I just use that. CPU PECI seems to be some sort of average or entire die temp, which should be fine in most cases.

  • How does this, as you say, directly answer [the] question because it basically repeats @benwiggy’s comment about it being irrelevant but never actually answers the question of which sensor represents the CPU? – Allan May 16 '20 at 11:49
  • Allan, At0mic says that CPU PECI is kinda the average of all of the cores. That’s what I was using earlier so I’ll go with that. Thanks! – Samarth Kabbur May 17 '20 at 2:08

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