It shouldn't really throttle to 1ghz - it's because Apple puts low quality paste in it, and sometimes because of dust.
My Macbook from 2014, is still excellent but it started throttling to 1ghz with video encoding.
After going to a repair shop and telling them about the problem they put high quality thermal paste in it for about 100 usd and the problem disappeared. Now i get 100% CPU no matter what i throw at it, pretty incredible with a computer from 2014!
Thanks for your experience, but the passively cooled 12" Macbook is really a different thing. Basically, it isn't a 2.5 GHz CPU that throttles, but a 1.1 GHz CPU which can boost itself for a very short time, and the it runs into thermal limit and returns to a 1.1 GHz sustained performance.
And on hot day, that boost might last 30 seconds and then that's it.
My Macbook from 2014, is still excellent but it started throttling to 1ghz with video encoding.
After going to a repair shop and telling them about the problem they put high quality thermal paste in it for about 100 usd and the problem disappeared. Now i get 100% CPU no matter what i throw at it, pretty incredible with a computer from 2014!
Just fyi..