[msbarnett]

TSMC doesn't have a 22nm process -- they offer a 20nm process instead, but it was heavily delayed, had huge yield issues, and most of its production capability was double-booked with Apple, all of which meant it wasn't feasible to use in time for Nvidia's previous generation (Maxwell) launch.

Maxwell had been planned as 20nm, but when TSMC couldn't solve their process issues the first Maxwell was taped out at 28nm (GM107 aka the GeForce 750), while they waited on the rest of lineup. 6 months later, with TSMC still having issues at 20nm, the GM204(GeForce 980/970) was launched at 28nm.

16nm FinFET wasn't subject to massive delays (it launched early, in fact), and seems to have better yields than 20nm early on, so Pascal skipped right down to it.

[kosmic_k]

Thanks for the explanation! I haven't been following fab process news for some time so I've been very much out of the loop.