How to disable 2 cores on a quadcore i7?

I have a laptop with a quadcore i7 that runs hot. I don't need 2 of the cores. How can I shut them off?

mmm bacon

Posted 2010-07-21T20:22:25.183

Reputation: 359

3Why? (15 chars) – Hello71 – 2010-07-21T20:28:38.187

What operating system ? – Paul R – 2010-07-21T20:29:02.443

With 2 fewer cores, I assume it will run cooler and the fans won't come on as often. It's Windows 7 x64. – mmm bacon – 2010-07-21T20:34:39.720

Maybe, maybe not. Either way, we need to know more about your laptop. What manufacturer/model is it? – squircle – 2010-07-21T20:37:08.887

It's an HP Envy 15 with an i7-720QM Quad Core processor (1.6GHz, 6MB L3 Cache) with Turbo Boost up to 2.8 GHz. ATI 5830 GPU. I would have bought the i5 model, but it's only sold with an i7 these days. – mmm bacon – 2010-07-21T20:53:35.623

More Cores <> More Heat, Higher CPU Usage = More Heat, Less Cores + CPU Intensive Task = More Heat, Same Cores + Better Ventilation = Less Heat, You may want to try and disable Hyper Threading in the BIOS if that's an option. – kobaltz – 2012-07-04T19:36:43.597

Answers

You can't command the processor to disable the cores, the only thing you can do to avoid the heat is going for another processor or to check that the processor is sufficiently cooled.

Tamara Wijsman

Posted 2010-07-21T20:22:25.183

Reputation: 54 163

Actually you can do it with core parking. Look for my answer. – Waldemar Wosiński – 2016-11-24T15:20:22.320

Many computers have BIOS options to disable cores. You can also disable hyper threading which is also disabling cores, though I doubt that would improve cooling much. A final thing that could be done is in Windows itself. Go to the Advanced Boot Options (msconfig > boot tab > Advanced options) and specify the number of cores you want to use. I would personally not recommend any of these solutions as it is basically castrating your machine. Find a better cooling solution or practice better usage of your machine such as using it only on hard surfaces, cleaning the dust out of the vents, using a cool pad, ect. You might also want to check for a BIOS update that will turn the fan on more often or use something like SpeedFan to manually control your fan speed and thus increase your cooling potential.

ubiquibacon

Posted 2010-07-21T20:22:25.183

Reputation: 7 287

@TomWij I do not have that laptop (do you?) so I don't know what the BIOS options are. I see more and more new computers with options like this available in the BIOS, and there is nothing wrong with listing possible options for the OP. Please do not take it personal (I didn't down vote your answer) but you made a blanket statement, which was not entirely accurate, I simply pointed out the inaccuracy. As for the advanced options, if you disable cores how I said they will not register in the device manager, so my statement is true. I don't know what you mean about "only" affecting boot. – ubiquibacon – 2011-01-22T19:44:49.913

Ah, in that way, sorry... Well, it's located under the boot tab so it only effects the boot phase. During which Windows detects all cores and from that point they should all be used instead of a single one. @mmmbacon confirms this in his comment, but interesting enough: I don't know about the effect towards device manager, they shouldn't disappear but I haven't checked...

– Tamara Wijsman – 2011-01-22T21:14:31.887

The Intel i series tends to do this. They have a certain thermal limit built in and basically manage the system such that: if you are running on all cores, it manages speed among them and tries to run the system as fast as it can without overheating. If you aren't running all cores, it will shut down the cores that aren't used and try to overclock the cores that are used - up to the thermal limit. Note that it TRIES to overclock and this creates heat.

Blackbeagle

Posted 2010-07-21T20:22:25.183

Reputation: 6 424

Right, but is there a way to manually disable 2 cores? Turbo mode on this system never seems to turn on. – mmm bacon – 2010-07-21T20:35:43.103

@mmmbacon: No, there is no way to disable them. Why would you spent a lot on a processor to downgrade the performance afterwards, I would rather fix the cooling instead. – Tamara Wijsman – 2011-01-22T18:39:38.693

In Linux/Ubuntu, just run this:

sudo sh -c "echo '0' > /sys/devices/system/cpu/cpu1/online"

Replace cpu1 with cpu2 and so on to turn off more cores. And to turn them back on:

sudo sh -c "echo '1' > /sys/devices/system/cpu/cpu1/online"

Sepero

Posted 2010-07-21T20:22:25.183

Reputation: 266

Go to Run, type in msconfig, go to Boot tab, click Advanced Options, and select "Number of Processors". Then change it to half of the list (Pick 4, because you have 8 threads = 4 cores, so 4 threads = cores). Reboot ;)

Hao Zhang

Posted 2010-07-21T20:22:25.183

Reputation: 11

Thanks. I tried that originally. Even though this kept Windows from using additional cores, I'm pretty sure the cores were still on and consumed power. – mmm bacon – 2010-11-07T15:16:23.907

Sadly, this only affects the boot phase... – Tamara Wijsman – 2011-01-22T18:40:25.197

You can do it with core parking.

By setting performance core parking max cores you set how many cores will be parked all the time. Here you can check how to do it.

With this solution you can turn them on/off whitout reboot.

Waldemar Wosiński

Posted 2010-07-21T20:22:25.183

Reputation: 431

While I realise its a pretty long blog post, could you post the essential parts of it here? If your blog goes down or is reorganised, your answer essentially becomes useless. – Journeyman Geek – 2016-11-24T14:05:11.150

It is advanced technique. Without context it can harm the user. I added some hint for power users. – Waldemar Wosiński – 2016-11-24T14:50:59.713