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Zenbook UX325EA weird thottle coming back to and from AC mode

Star II
System: Windows 10 Home
Battery or AC: both
Model: UX325EA
Frequency of occurrence: always
Reset OS:
Screenshot or video:
Detailed description:
When i start my laptop the CPU is 90% of the time at a nice high speed on OC and super stable, whether it's on AC or also on battery - in high performance mode, and "performance" from the Asus app, great!! for instance i get 4.05 - 4.35 - 4.50 ghz.
BUT when i unplug AC then it drops down noticeably. Even if i am on battery FIRST stable on 4.3ghz then I plug in the AC then it drops. it seems when there is a "change" in power source, there is a drop or something triggers.
Why does this happen?
During these times, laptop wasn't under pressure or load or anything at that time, so is really cold and cool, no temperature increase (which i know affects the tiny zenbook), so why does the clock drops so much when you change the power source? either on battery TO AC or AC to battery? simply by unplugging or plugging it? all intel power savings are switched off.
is that because the machine thinks that during AC operation it might overheat? then if i restart it goes again to high frequency. or just cycling on and off hibernate 2-3 times, which is what i do most often, sometimes it even takes 4 cycles of hibernation, which are fast anyway since it's a very fast laptop. Still is it possible to avoid this?

Star II
no, it's a bit odd, when i start up or after a restart i get a nice high clock 4.30 4.50 4.60 ghz stable (also under stress to a degree) BUT as soon as you plug AC in then it drops to let's say 3.60 - 3.80 - i know small difference but you can see that it's not instant super fast as it CAN BE.
if you do, as a trick cycle in Hybernate 2-3 times, sometimes 4 then you get the high clock again or you can do a restart but then lose all the work, i want to know WHY.
Likewise, when you start the PC with AC connected and do get the high cpu frequency, when i unplug AC then it drops, but this is more understandable.
I am using a klim coolpad for the little zenbook and this works fantastic when on AC, even under stress this little monster keeps high frequency as i gave him basically 50% extra cooling and cooling is such an issue for this machine, although not designed for this. (as long as you don't unplug AC)
So in case you're wondering you can squeeze extra performance out of the Zenbook if you give him extra cooling, i tested 5 cool pads and this one i have now is great. always around 40-60 C even under stress, normally would go 90C and then CPU frequency drops bigtime.

Star II

If it goes back again when you run demanding apps then it's likely normal behavior. Why this might happen?

  • Higher frequencies require higher CPU core voltages to keep the core stable.
  • Power consumption is proportional to: V^2 * freq
  • Doubling the voltage would result in roughly ~ 4x power draw on the same frequency.

For these reasons it makes perfect sense to scale down the clock (and voltages) when the core is idling especially on battery power.

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no it doesn't behave that way when you use high performance, it does that in balanced, but that's boring mode when i am near AC i want max power all the time, it makes me more productive. this laptop is so fast when it's on turbo all the time, with such a fast ssd as well
it's just this dropping sometimes annoying, but overall i love it 😉

Star II

So your laptop will lock to a lower frequency and never or barely goes above?

And every time you plug or unplug the charger it will drop even lower?

View post
NO, read the other comment i just added, maybe wasn't clear explanation earlier.

Community Legend II
Hello Gabrio,
May I know your current BIOS version?
And if possible, can you reproduce the issue and video record it?
Thank you so much.

Star II
hello, i made a video, please have a look, i have to do this since it doesn't want me to post links:
d r o p b o x . c o m /s/6a2ssyb5pg5xm29/Zenbook%20CPU%20drop.mp4?dl=0
just remove the spaces in the popular file sharing platform domain name 🙂
i have the latest BIOS so version
do you have a machine there to test this with also? maybe it's not supposed to stay all the time at MAX turbo.
Although when it's on AC, performance mode and with proper cooling, it can perfectly do it. I keep it 10 hours on that and works 100% all the time.
thank you,