Question 9900KS Downclocking Under Load


Jan 13, 2017
I have a 9900KS that downclocks from 5.0GHz to 4.5GHz when under heavy load using Intel Burn Test & Prime95.

I have an MSI MPG Z390M GAMING EDGE AC Motherboard and adequate liquid cooling, it doesn't go over 70°C.

Are there any MSI Mobo settings that I need to adjust to keep my frequency from dropping?
Always wondered why people want to buy these high end power hungry heat monsters and use micro atx or itx motherboards with them and cramp them in small cases.

Also I’d say 70c is pretty high if it’s only running at 4.5. Mine is overclocked to 5.0 all cores and hits 81c on full stress.
What is the make/model of your case and cooling fan arrangement?
Good cooling starts with good intake airflow.

Does your aio cooler take in cool air from the outside?
That is best for cpu cooling, but not so good for motherboard and graphics cooling.

You can specify a multiplier reduction if the workload contains AVX instructions.
AVX is a heat producing instruction, and is present in stress tests like yours.

Try using the intel performance maximizer app.,6179.html
Normal behavior for many mainboards is to downclock after a 15-20 sec burst to something less to maintain the 127 watt TDP...; some mainboards ignore this, but, this behavior (specifically) does not indicate a problem in itself.

Look for TDP constraints/power limits in BIOS, and remove them....but, be prepared for more heat