Intel CPUs are designed to work like 100% load 24/7 for many years when run at standard setting and with standard cooling method. I cant see what is to be gained by reducing the processor performance by underclocking - what do you want to achieve by this?

If you pay for a chips performance, why would you want to reduce it instead of buying a cheaper lower performance chip?

If you want to undervolt / underclock then I guess in theory it would be similar to overclocking but in reverse. You need to watch your stability as you'd be reducing the voltages below the level set by the CPU manufacturer to make then perform correctly