Possible to disable cores?

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multiversemeep

Jun 17, 2018
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Hi, I am looking to build a laptop (Yes, I know it's crazy, but don't hate me), and I was wondering, is it possible to disable cores on an intel cpu, and will it draw less power? I've been doing research for a while on this subject, but can't find anything. I currently have an AMD processor, so I can't test it .-. Thx in advance.
 
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photonboy
Agreed.
The screen probably uses a big chunk of the power.

Disabling cores might make no difference or even make things worse. If you have more cores then power management can keep the voltage lower per core so in theory the power draw on two cores running 2x the processing tasks might draw more power than four cores running half of what the two cores does on average.

Really depends on what you're doing but frankly there are several POWER OPTIONS you can look at related to the CPU maximum, screen brightness etc that you would look at instead.

*and why "build" a laptop where you are considering to disable cores anyway? Why not use a higher capacity better and/or use the proper CPU for the job? It would cost MORE money to buy a CPU...
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photonboy

photonboy

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Jun 20, 2006
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Agreed.
The screen probably uses a big chunk of the power.

Disabling cores might make no difference or even make things worse. If you have more cores then power management can keep the voltage lower per core so in theory the power draw on two cores running 2x the processing tasks might draw more power than four cores running half of what the two cores does on average.

Really depends on what you're doing but frankly there are several POWER OPTIONS you can look at related to the CPU maximum, screen brightness etc that you would look at instead.

*and why "build" a laptop where you are considering to disable cores anyway? Why not use a higher capacity better and/or use the proper CPU for the job? It would cost MORE money to buy a CPU with more cores so then disabling them makes no sense.

**also "testing" may not help. Modern CPU's are more power efficient than older CPU's so disabling cores on an older setup might actually use less power but disabling cores on a newer system might instead draw MORE when under heavier loads.
 
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photonboy

photonboy

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Jun 20, 2006
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It occurs to me you may be planning a GAMING oriented build then want to occasionally disable some cores in the BIOS for when your demands are light?

I think that for very LIGHT usage it would make a small difference but probably not enough to worry about. Mobile power management is pretty good now in "PARKING" cores and dynamically lowering the voltage to reduce CPU power consumption.
 
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geofelt

geofelt

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Oct 9, 2006
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If you want to test such things out, you can disable some threads in the windows startup options.
You can do this in the windows msconfig boot advanced options option.
You will need to reboot for the change to take effect. Set the number of threads to less than you have.

Windows power options will reduce laptop screen brightness and cpu power when running on battery power.
You can adjust this as you wish.
 
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photonboy

photonboy

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As I said though, testing this on an older CPU might not be applicable. For example, older CPU's where very slow to PARK the cores but modern CPU's are much faster so having MORE CORES ENABLED is less problematic when you can park cores as well as throttle the remaining ones efficiently.

A task running on a CPU core which needs to run process twice as much (because you disabled half the cores) could raise the voltage (thus power) in a way that's less efficient than running over two cores at a lower voltage.

I'm no expert but I'm just saying it's probably pointless, again considering that modern CPU's are so great at parking and dynamically throttling voltage/frequency on un-parked cores.

EDIT:
My post above should have said "battery" as in higher capacity battery not "better"
 
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geofelt

geofelt

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Thinking about this a bit more.
Reducing cores will not make any difference unless the app can fully load all cores.
Windows will distribute cpu activity across the cores it has available.
If you have an app that can only use 2-3 threads, your power consumption on an 8 thread processor will be the same if half are disabled.

I like to play civ 2.42 on long airplane flights.
It is a single threaded game that is poorly coded.
The cpu runs at 100% looking for keyboard input.
It looks like 25% busy on a quad core processor.
Normally, this gave me only 2-3 hours of playing time.
I reduced the max cpu busy % down to 30% and the game still played fine and I upped my battery to some 5 hours.

Ultimately, long battery life is better addressed by using a modern cpu that might consume 10w.
 
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