[T-Mobile Samsung Galaxy S 4] GameX2:
Hi,

I'm using a Canadian Galaxy S4, SGH-I337M.

Rooted, running on Liquidsmooth 4.4.4 ROM. Also has Ktoonsez kernel. It is currently undervolted+underclock a bit, and is stable (I could overclock it, but I don't. No need).

Been wondering for a long time about the operating CPU temperatures of the Galaxy S4... Never had the possibility to do testing with CPU temperatures before. I do have a LG P500 that I have overclocked a ton in the past, still work just fine, but the LG P500 is old and do not support viewing CPU temperature, so it's my first time experimenting with that.

How hot would be too hot for this phone? There are several opinions, but never figured out if I... "minimize" the risks of my actual temperatures, for some reason. My laptop CPU throttle at 85 celcius for instance. While it's a phone, it's completely different.

At night, while connected to charger, it would be pretty cool, at 25-30 degrees when I wake up;

I would say that most of the time, my CPU is running at 50 celsius, and rarely ever exceed 65-70 under normal use, or even gaming. Plus, the CPU is undervolted and a bit underclock, so I do feel like it run cooler than usual.

Quoting Meowmix from Rogers forums:

So, the case does matter? I do have that Otterbox case which is pretty tight and enclose the phone pretty well, I would believe that the phone would get less.. air.. but I mean, it's just a case, didn't thought it would affect much..?

Quoting Ahmed from AndroidCentral Forums, I would say that I have a quite similar situation.

I CAN reach 80-90 celsius, but only if I really want it to happen. 38 celsius for the battery is also correct, I never exceeded 41 degrees yet, on any Android phone (I don't know the dangerous battery temps.. But when I reach 40 degrees I try to put it down as fast as possible). With benchmarks, usually at the max frequency, or testing my undervolt with Stability Test, I CAN reach 80-90 celsius, which look really high. Additionally, I would remind that I don't overclock, and the CPU is undervolted so seems a bit cooler.

So on AndroidCentral, this is the reply Ahmed got, from "CR6" user:

THAT dangerous? Well, I don't phisically feel the heat - I do feel it, but since I have that phone case, that doesn't hurt at all. But like I mentionned, I never reach 80 celcius or more unless doing benchmarks. Usually I never exceed 65-70. But still it left me wondering - Why does Android allow such high temperatures in first place? Isn't the system suppose to shut down at some point in case of danger, and when?

I've also experimented with thermal throttling in the Ktoonsez kernel, and the throttling values of the ROMs. Touchwiz Stock ROM with DVFS disabled, seems to throttle at 80 celsius, look decent. Liquidsmooth AOSP ROM, stock kernel, does not seem to throttle at all (Huh)! Once, and that was exceptionnal, I've reached 100 CELSIUS using Wifi, connect to a charger after like 2 hours, room temperature was very warm, was not surprised, but when I noticed I reached 100 CELSISUS, I was WOAW, I should shut down. I did reached 100 degrees again, using Stability Test at max frequency after a few minutes. Needless to say I manually stopped the test, because I had no idea how much heat the phone could handle...

So been aware of this, "Ktweaker" app, for the Ktoonsez kernel I use now, does have a thermal throttling option, but I wondering which thermal value should I enter for best "performance"? Default was 70 degrees, I set mine at 80, I've heard of people even putting 90 for the same kernel. Besides, maybe I worry about it too much, because in no way the phone should exceed 70 degrees celcius under normal use anyway, or even gaming. Only way to reach insane temperatures would be benchmarking/stress testing...

Still, first time seeing these CPU temperatures also. I've overclocked my LG P500 several times in the past, dealing sometimes with random reboot, so make stability/overheating questionnable, but the device did not supported seeing the actual CPU temp. So I don't know which temperatures would be considered normal - probably, nothing above 75-80, correct (For the Galaxy S4, actually)?

At which point is the device supposed to shut down? Is that in the kernel or a hardware CPU trigger? Because heck, I've reached 100 degrees 2 times, I mean, how far/close was I from a shut down? I'm quite surprised.

I've also read of people complaining of S4 overheating, especially maybe after it was released - It's possible that it heats up more than other phones, but honnestly I have no idea.

Thanks for your answer =)