There are several different companies that design microprocessors. There is Intel, AMD, Imagination (MIPS), and Oracle (Sun SPARC) to name a few. However, none of these companies is known exclusively for their power efficiency. One company that does specialize in energy efficient processors is ARM.
Marvell launches 64-bit octa-core ARMADA Mobile PXA1936 SoC
Some people are worried about the "future proofing" of the Note 4. The worry seems to be that, if Samsung keeps the Note 4 as 32-bit only, when some models are capable of running in 64-bit mode, then the Note 4 has no future, it is doomed. Such thinking really isn't warranted. Let me explain.