One possibility is to reduce voltage for some percent and then power consumption reduces by square of the amount, which means you can have chip at 50% speed but draining only 25% power. That is significant only when network percentage increases so much that the chip can not earn its consumed power. But then reduced speed chip can still work for prolonged period and keep bringing profit because it consume much less power. If they made chips that can work on very low voltages as well as nominal, and possibly have other tricks with turning on and off portions of chip that does not need heavy power it may give significant advantage and increased return of bitcoins that chip would make before its discarded as obsolete. I'm only guessing here tho.