If a MacBook Pro runs hot or shows high kernel CPU, try charging it on the right

Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by fwip on Thursday April 23, 2020 @04:09PM (#22960632)

I switched from a Macbook pro 13" (2015) to the 16" this year. It's much noisier in day-to-day usage, which I've tracked down to high heat generated by the discrete GPU whenever it is in use (regardless of load).

Unfortunately, some conditions force the discrete GPU to activate - one of which is "being plugged into an external monitor." Even if you've only got terminals open, the GPU runs real hot with 1% load, and the fans ramp up to match. (This may only be true for some monitors - my work-provided monitor is the Apple Thunderbolt Display).

Sometimes Slack forces the discrete GPU to turn on, for example when clicking on an embedded youtube video. The discrete GPU will remain in use until Slack is restarted. Other applications sometimes behave similarly - I use https://gfx.io/ to see what applications are forcing it on.

Perhaps the cooling engineering is better, but the practical effects of it make me miss my 13" laptop.

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by magicalhippo on Thursday April 23, 2020 @04:40PM (#22961070)

> Unfortunately, some conditions force the discrete GPU to activate - one of which is "being plugged into an external monitor."

Had something similar with AMD (desktop) GPU some years ago. It wouldn't go to the lower power states if my desktop refresh rate was set above 119 Hz. So it would be hot and fairly loud. So I ended up using 119 Hz on the desktop and configure games to use 144 Hz.

I also noticed that the video card wouldn't decrease the RAM clock rate significantly, but when on the desktop reducing the RAM clock a lot had a very noticeable impact on heat and no measurable performance degradation. The answer I got for that was that it was tricky to dynamically scale the RAM to such a degree (IIRC I set it to half normal speed). I ended up using an overclocking tool with profiles, worked fine.

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by bouke on Thursday April 23, 2020 @05:48PM (#22961925)

Someone posted somewhere that switching to an usb-c monitor fixed their issue (instead of usb-c to hdmi adapter). Anyone here have some experience with this?

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by fwip on Thursday April 23, 2020 @06:41PM (#22962399)

This doesn't answer your question, but I'm using an Apple-provided USB-C -> thunderbolt 2 adapter, as it's the only input that my display will accept.

It's frustrating that this problem is present with all-Apple hardware.

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by mthoms on Thursday April 23, 2020 @06:43PM (#22962417)

Same issue here moving from a 2016 13" to the new 16". It's silly that we can't just use the integrated intel GPU with an external monitor if we desire.

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by tomaskafka on Friday April 24, 2020 @08:14AM (#22967112)

Ugh, thanks. I was eying larger MBP as my 2017 13" runs almost always with both cores used, and is loud - was hoping a six core would be quiet under same load :/.

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by mthoms on Friday April 24, 2020 @04:59PM (#22972844)

Now that I think about it, lately it's been fine. Fans don't come on when powering an external 4k monitor under normal use anymore.

However, I'm not sure whether that's due to a recent software update or the fact I recently switched the cable I use from HDMI to DisplayPort.

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by the_pwner224 on Thursday April 23, 2020 @04:16PM (#22960708)

This was also true for me on a 2012 MBP (on HDMI and DisplayPort iirc).

My XPS 15 had a similar issue where turning on the GPU made it heat up and become loud - actually the discrete GPU offered no performance increase because the heat made everything throttle....... sad! At least I could use an external monitor with that one though.

It's just a limitation of the laptop form factor. My desktop has a 45 watt processor, same as the i7s, and it has a huge block of metal and a 120mm fan to keep it cool quietly (but still audible under load). There's no way to fit a 45w CPU and 45w GPU into a laptop and make it work.

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by fwip on Thursday April 23, 2020 @06:39PM (#22962386)

I'm okay with the fans spinning up loud when I'm doing something intense! I expect that transcoding video or `make -j12` will put out a lot of heat.

I'm frustrated because the fans often spin up loud when GPU usage and CPU usage are both below 10% - when I'm literally just reading my email.

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by drevil-v2 on Friday April 24, 2020 @03:47AM (#22965628)

This happens with MS Edge browser too. Just browsing to Arstechnica, for some reason, turns on the discrete GPU and it will stay on until Edge is shutdown or restarted.

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Re:If a MacBook Pro runs hot or shows high kernel CPU, try c... by dharma1 on Thursday April 23, 2020 @06:12PM (#22962164)

I went back to 13" mbpro for same reasons

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