Not necessarily. From what I've read the Core M line is mostly TDP limited, not heat limited. The top-end single core burst speeds are possible due to Broadwell being allowed to massively exceed it's TDP limit for very shorts bursts (which is out-lined in Broadwell release literature). The Z20t can, if I'm reading the benchmarks right, sustain ~1.7Ghz on the 5y71 model when using the keyboard and plugged into a mains outlet and I doubt that the 5y71, fan or no fan, can go much higher than that at 100% load without grossly exceeding 6w. Although I'm only going by extrapolating benchmark numbers so someone may wish to check the actual max sustained clockrate. I would love to check what my 5Y51 model can do but it's stuck in courier hell atm. If it gets delivered today then I'll post some clock speed numbers on here later.