[SOLVED] CPU speed dropping to 800Mhz while watching youtube videos ?

[I Mess With Windows]

Hello,
I have a Dell Inspiron 1520. I know this is a fairly old laptop, but I have laptops older than this and they can play youtube videos just fine.
Here are the hardware specs of my device:
Intel Core 2 Duo T9300
Intel Mobile 960 Express Chipset Family
4GB RAM DDR2 667Mhz

I am running windows 10 on this laptop, and I didn't have any issues for several months. Now when the CPU temperature reaches about 60 degrees (read by CoreTemp), the CPU frequency drops from about 2.5Ghz to less than 800Mhz, causing my youtube video to become just unwatchable.
Installing the SSD of another laptop that's running windows 7 in it, my YouTube videos played just fine. I downloaded CoreTemp here too just to check the CPU frequency vs temperature, and for a temperature of about 50 degrees (which makes sense as windows 7 requires less resources), the frequency moves a lot from 800Mhz to 2.5Ghz, but it never gets stuck at 800Mhz and my videos play just fine.
So this is clearly a software side problem.
Is there any way I could tell windows 10 to keep the frequency high even when the CPU temperatures reaches the reasonnable frequency of 60 degrees?

 

[lvt]

The T9300 comes with SpeedStep feature that reduces your CPU speed when it feels necessary to do so.

Try to disable SpeedStep by selecting your Power setting to something like Desktop, Always On etc...

 

[I Mess With Windows]

Interesting... how do I do that? Just tried a T7500, the issue is gone. But I want to keep the T9300 because its frequency is 2.5Ghz, and the T7500 frequency is only 2.2Ghz, and also because the T7500 runs much hotter, I reach 80 degrees on youtube playback

 

[I Mess With Windows]

Basically the CPU runs fine, 200Mhz with 12.5 multiplier, but as soon as the temperature goes a little bit up, the frequency gets down to 130Mhz and 6 multiplier.
Just found SpeedStep in the BIOS of my computer, and disabled it. Now when the load is light the CPU runs at about 1.6Ghz (200Mhz with 8 multiplier). Watching a YouTube video in 1080P, it appears to play fine, but the frequency is stuck at about 1.6Ghz. It doesn't change as the CPU gets hot.
So it's better but I still don't get my constant 2.5Ghz.
EDIT: it doesn't actually play fine, I often get errors

 

[I Mess With Windows]

Tried to enable SpeedStep again and set the advanced windows power setting to 95% minimum CPU power, but it didn't help at all.
For anyone thinking this is a BIOS issue, the BIOS recognizes the CPU just fine, it says Penryn.
However, my BIOS is only A04, while I could update it to A09, which I will do and see if it fixes my problem.

 

[I Mess With Windows]

The BIOS update fixed it. Thanks for your help cause without knowing about the SpeedStep I wouldn't have the idea of updating the BIOS.