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?
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.
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.
Try Bitsum Lasso: https://bitsum.com/
It can manage your cores and lower them to what you desire. Also download ParkControl, to control when your CPUs are idle.