CPU's Not being used while building source

Hi There,

I am building c++ from the source. I have done this a few times now, and it always seems to take a few hours. (4+) This seems very long. Especially since I am using a decent system. I Got an SSD, 12 cores (20 logical), and 32 Gb of ram.

What I am noticing is that my actual CPU usage is strange. Out of the 20 logical cores, 16 are close to idle or even parked. And four are running at 100% all the time.

I am using Fastbuild. And in there, I can see that it uses 19 cores. And that some of the files take 800+ seconds to build.

Does anyone have any idea what is going wrong? I would appreciate some help.

Okey So Am still doing some research on this issue.

My build config is

<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
	<BuildConfiguration>
		<bAllowFASTBuild>0</bAllowFASTBuild>
	</BuildConfiguration>
	<ParallelExecutor>
		<ProcessorCountMultiplier>1.6</ProcessorCountMultiplier>
		<MaxProcessorCount>12</MaxProcessorCount>
	</ParallelExecutor>
	<FASTBuild>
		<bEnableDistribution>0</bEnableDistribution>
		<bEnableCaching>1</bEnableCaching>
		<CacheMode>ReadWrite</CacheMode>
		<FBuildCachePath>C:\Users\rene\Desktop\FastBuild\Cashe</FBuildCachePath>
	</FASTBuild>
</Configuration>

My CPU is a i7-12700k So I got 12 cores 8 P-Cores and 4 E-Cores

I have tried changing a lot of things. Still, it uses only 4 cores.

CPU

The problem seems to be Windows 10 with E-Cores. Disabling them in the bios made my other core’s P-Cores run at full speed.

Another solution should be updating to windows 11.