Actually there is plenty of precedent for that conclusion. Scaling CPU cores up (=efficient but high performance cores) is super-hard -- making low-power cores is pretty simple in comparison --; almost everyone fails or failed at it. Currently there are two companies on the planet that do that sort of thing, and not so long ago it was only one. Notable names that failed hard in this are: Intel, DEC, Sun, Fujitsu, AMD, IBM, HP, Intel, as well as SGI, IBM and AMD.