That is quite common, an overheating inexpensive laptop that turns unusable because it's throttling constantly.
This little guy was insanely slow, reaching more than 80°C, throttling like crazy. My first clean win10 install took 2 fucking hours on the stock HDD... At first inspection, it wasn't even dirty or full of dust. So I put in a 240GB SSD, put a 1TB drive in the DVD tray, and installed win10 in 7 minutes. But it was still overheating and throttling like crazy.
Inspecting the so called "cooling system"... that non-thermal-anymore-thing was solid, like ceramic. The heatsink is obviously too small, so is the fan (wich is by the way incredibly noisy considering its size). I can't nor want to change them right now, but I will think of a better solution later.
For now: new real thermal paste.
While the case was open, I improved a little the air flow to the tiny fan a little better. Just some cutting and sanding. That is actually improving the airflow to the fan by 33%.
The laptop was flat on my desk, and despite a slight improvement, temperatures were still bad and throttling still occured. There was absolutely no air flow under that laptop... I made a stand out of aluminum corners, that would allow me to test various fans and fan ducts beneath the laptop. Also, some undervolting was definitely needed: I created 3 modes in Throttlestop:
- performances, sticking to the turbo x31 @ 3.1Ghz as much as possible,
- a "silent" battery mode mode with max x30 turbo,
- and a battery mode with turbo disabled.
All set to -145mV for the core and -100mV for the cache and GPU. I tweaked the TPL so the CPU sticks to the x31 multiplier in performances mode with no limits or throttling. The room temp is 22.5°C, after 25min of cup-Z stress, core one reached 60°C, sticking to 3.1Ghz.
Next step was making a prototype fan to force cool air in the case. Made that fast and dirty out of cardboard, a noctua 8cm and 12V power supply. It is quite noisy, and the temperatures don't really improve: the gain is barely 2°C, not worth the noise. Here is a cpu-Z stress run, then cinebench multi and single core. The CPU stayed locked at x31T.
The results were the same with a 12cm fan. Not very impressive and noisy. Not worth the hassle. I prefer less noise over barely 2°C temperature drop.
I got the best temperature drop (-7°C) with a super noisy 80CFM 8cm fan. NO WAY I'm gonna use that.
So, The laptop is staying on its little stand, and working much better than it used to.
Using this laptop in performance mode is now ok: no more throttling, the CPU remains steadily at 3.1Ghz and max temperature delta is now more or less 40°C.
In Silent battery mode, the CPU can remain at 3.0Ghz when needed, and delta T is 35°C.
In battery mode, I disabled the turbo, and the CPU hits 2.5Ghz, delta T is more or less 30°C.
The benchmarks are pretty good for an i5 7200U, thanks to the CPU being locked on x31T under load, and the Nvidia 920MX 2Gb GDDR5 overclocks pretty well.
Now, I still have to think of a real better cooling solution, and especially a better fan. Than things is not really super noisy per se, but there are two super annoying frequency spikes arround 2.1Khz and 4.2Khz. I hate that.