# Is it possible to limit the cpu usage of the lightmass build?

**URL:** <https://forums.unrealengine.com/t/is-it-possible-to-limit-the-cpu-usage-of-the-lightmass-build/390204>\
**Category:** Rendering\
**Tags:** bake, Lightmass, ram, baked-lighting, unreal-engine, CPU, question\
**Created:** [April 7, 2017, 1:43am UTC](https://forums.unrealengine.com/t/is-it-possible-to-limit-the-cpu-usage-of-the-lightmass-build/390204 "2017-04-07T01:43:52Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![anonymous\_user\_0e0dcd18](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_0e0dcd18](https://forums.unrealengine.com/u/anonymous_user_0e0dcd18)\
**Post date:** [April 7, 2017, 1:43am UTC](https://forums.unrealengine.com/t/is-it-possible-to-limit-the-cpu-usage-of-the-lightmass-build/390204/1 "2017-04-07T01:43:52Z")

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Hi,

I have a laptop that I use to build lighting in my scenes, and I’d like to keep the cpu temp lower than it is for the duration of time spent baking lightmass. Would it be possible to limit the cpu usage to something like 75% rather than 100% of available cpu power? Obviously, it’ll take longer to bake, but I’m fine with this. Also, ram of course is no issue. 48gigs on board, if that’s relevant.

Thanks

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**Author:** ![TurtleSimos](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@TurtleSimos](https://forums.unrealengine.com/u/TurtleSimos)\
**Post date:** [April 7, 2017, 8:28pm UTC](https://forums.unrealengine.com/t/is-it-possible-to-limit-the-cpu-usage-of-the-lightmass-build/390204/2 "2017-04-07T20:28:45Z")

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Open Swarm Agent. In settings, enable Developer Settings. Then the developer settings tab has two settings - “LocalJobsDefaultProcessorCount” and “RemoteJobsDefaultProcessorCount”. These control the number of threads Lightmass will use for local builds, or network ones. These numbers include hyperthreading - so if you have a 4 core i7 with hyperthreading, you have 8 available. In that case the default “LocalJobsDefaultProcessorCount” will be 7 - the default for local builds being all but one processor core. Change that to 6 and it would use 3+3 (hyperthreading) cores, so 75%.

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**Author:** ![anonymous\_user\_0e0dcd18](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_0e0dcd18](https://forums.unrealengine.com/u/anonymous_user_0e0dcd18)\
**Post date:** [April 8, 2017, 11:06pm UTC](https://forums.unrealengine.com/t/is-it-possible-to-limit-the-cpu-usage-of-the-lightmass-build/390204/3 "2017-04-08T23:06:51Z")

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Thank you!

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**Author:** ![SullenSecret](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@SullenSecret](https://forums.unrealengine.com/u/SullenSecret)\
**Post date:** [August 8, 2018, 12:31pm UTC](https://forums.unrealengine.com/t/is-it-possible-to-limit-the-cpu-usage-of-the-lightmass-build/390204/4 "2018-08-08T12:31:02Z")

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You can also down-clock your processor, but that requires learning how to do it in the BIOS settings.

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**Author:** ![motorsep](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/motorsep/32/918698_2.png) [@motorsep](https://forums.unrealengine.com/u/motorsep)\
**Post date:** [December 2, 2023, 10:09pm UTC](https://forums.unrealengine.com/t/is-it-possible-to-limit-the-cpu-usage-of-the-lightmass-build/390204/5 "2023-12-02T22:09:41Z")

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Still a relevant thread!

I upgraded to i7-14700K from i7-7700 and while CPULM built lighting a lot faster (Preview quality, went down from half-day roughly, to 1hr 48m), it wasn’t using whole 20 cores of the new CPU. So I bumped up number of cores to be used.

 ![UE5 CPULM Swarm OG settings](https://d3kjluh73b9h9o.cloudfront.net/original/4X/4/c/e/4ce9d761d5f77ddb96a241d182186c02d080b4ea.png)  
While CPULM accelerated to 54% rapidly, after that it slowed down and eventually got stuck on 99%. All in all, instead of 1 hr 48m it took about an hour.