Overclocking is usually done in the computer's BIOS setup utility. Most brand-name computers such as Dell, HP, and others do not allow overclocking in the BIOS setup utility, but custom-built computers usually do. It is also possible to do the opposite, called underclocking, where the processor is run at a lower speed than intended. This may be done to extend battery life and reduce heat output. Underclocking will not usually damage a processor and may in fact make it last longer. Some processors automatically underclock themselves when the computer is not doing a lot of work.