1

I want to leave my Pi 3 on overnight doing a Mathematica calculation. What temperature would you say is too high to be at constantly for 8 hours? Would 65C be too high?

EDIT:

I am aware of the throttling temperature. However, I personally don't feel comfortable running my pi at a constantly throttled 85C for 8 straight hours, because of how it might affect the life of pi (Pun not intended). But seriously, is this worrying unfounded?

And suppose my fan solution keeps my temp at a constant 65C all night while doing benchmark level intensity calculations. Is this an ok temp for 8 hours straight? If so, perhaps I should overclock my pi so the calculation will run faster?

  • 3
    No, the Pi thermal throttles at around 85°C, so 65°C is not too high. I have left my Pi running for 2 months solid before without any problems, so one night is not going to be an issue. – Darth Vader May 7 '16 at 7:37
  • @DarthVader But was the processor running at 100% all night throttled at 85C? Would you be worried if it did? Also, what temp does yours idle at? Thanks! – Elem-Teach-w-Bach-n-Math-Ed May 7 '16 at 13:51
  • "If so, perhaps I should overclock my pi so the calculation will run faster?" -> Does not make much sense since overclocking will increase the temperature and going beyond 65C is probably not what you want. – goldilocks May 7 '16 at 14:09
  • @goldilocks If 85C constantly all night is safe, why am I calculating at only 65C when my pi could be running faster? – Elem-Teach-w-Bach-n-Math-Ed May 7 '16 at 14:11
  • 1
    WRT "What temp would you feel comfortable running your pi at all night?" I'd say whatever temperature it reaches while running 100% without overclocking, or in the case of the pi's where overclocking is still permitted under warranty, without doing to the point that requires overvolting. That's a purely subjective call though, I am not an EE. – goldilocks May 7 '16 at 14:21
3

Would 65C be too high?

Have you actually checked that it gets anywhere near this temperature? I have not maxed one out all night, but I occasionally do it for 30+ minutes while observing the core temperature, and even after an hour it barely rises beyond 50C. In fact, it seems to me that it stabilizes at that point.

This is in a 20-25C room, no overclocking, no heatsinks fans, etc. I may have done it with a B overclocked to 800 or 900 Mhz as well.

You should explore this before you assume that running at 100% will cause a steady linear rise in core temp. I do not think this is the case; it is more likely to be roughly logarithmic and plateau.

Also, damage due to temperature in electronics is primarily caused by either:

  • Exceeding a certain maximum, at which point internal components fuse. For the pi the OEM states this as 85C.

  • Oscillating expansion and contraction. In other words, if you can get it up to 65C (which probably requires overclocking and/or a high ambient temperature) by maxing the processor out for 3 minutes, and you do this, then allow it to cool back down, then heat it up again and so on, you are producing the greatest possible wear on the component. However, if the temperature stabilizes after 3 minutes and you leave it there for 4 hours, then this is not substantially worse than leaving it plugged in doing nothing for 4 hours. It is not expanding and contracting constantly.

There's a bit of idealization in the last point -- a pi left doing nothing will probably last longer than one constantly maxed out -- but the general principal holds.

What temp would you feel comfortable running your pi at all night?

Since pis are inexpensive and I buy them to use them, if that use included a desire to do intensive calculations all night I'd say whatever temperature it plateaus at. There's a related question about overclocking, since that will increase the temperature, and the question becomes largely subjective.

Personally, if it plateaued over 70C I would reduce the overclocking. This is mostly because laptops I've owned that ended up with overheating problems (because I let too much dust pack in) would get that hot repeatedly without damage, and my current laptop core temp seems to have the same idle temperature as a pi (45C). I think people who do a lot of desktop gaming will run systems with a lower idle temp (30-35C) at 70-80C for hours at a time. This is something you might want to explore by searching overclocker and gamer forums.

  • This seems much more like a comment as it didn't answer my question, but yes I've run the calculation for about 10 minutes with the temp seeming to peak at 63 with occasional flashes of 64. Mathematica really can tax the pi much like a benchmark, and this is a Pi 3, btw. I'm supposing my temp won't go higher than 65, but I've asked this question before leaving it on all night to see. – Elem-Teach-w-Bach-n-Math-Ed May 7 '16 at 14:04
  • 1
    Fair enough -- I've just edited in some more stuff about the effects of temperature that addresses the issue more directly. – goldilocks May 7 '16 at 14:07
  • As a further anecdote about this, I have an old ATI radeon card in my desktop to support a third monitor. I bought the card years ago to learn openGL with, but the fan on it was way too loud and only had one speed (on), so when I took it out of the closet this time I just took the fan off and managed to screw the northbridge heatsink from an old mobo on. I don't use it for 3D and it barely has to do anything but still averages 55-60C which is I think 10-15C over where it should be idle. I'm curious as to how long it will last, so far over 6 months, with it on 6-10 hours/day. – goldilocks May 7 '16 at 14:48
3

The Pi will run until internal temperature reaches 85℃ at which point it will throttle itself back by reducing clock rate.

  • I was aware of the throttling temperature. I personally don't feel comfortable running my pi at a constantly throttled 85C for 8 straight hours, because of how it might affect the life of pi (Pun not intended). But seriously, is this worrying unfounded? – Elem-Teach-w-Bach-n-Math-Ed May 7 '16 at 13:37
  • I'm going to edit the OP to reflect this. – Elem-Teach-w-Bach-n-Math-Ed May 7 '16 at 13:38
  • @Elem-Teach-w-Bach-n-Math-Ed It is unlikey to actually reach this temperature. I run my Pi continuously and even in Sydney summer (40℃ max) they rarely exceed 50℃. Running a processor intensive task may bump it up. There are monitoring programs which can monitor temperature continuously and display graph. – Milliways May 7 '16 at 22:45
  • Yes, but do you regularly use mathematica? Or anything that would max all 4 cores to 100% for an extended period? These easily bring the pi to a temp where it is thermal throttling at 85C within 10 minutes if not using some type of active cooling solution. – Elem-Teach-w-Bach-n-Math-Ed May 7 '16 at 22:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.