NVIDIA had about 5 different generations of Tegra before the K1 [1]. The A15-based K1 (T124) came before the Denver-based K1 (T132) AFAIK. Both are very nice and a clear improvement over the previous generations. Denver is a bit inconsistent in its performance, but on average it dominates A15s and A57s. Nexus 9, however, has very poor thermal design and can only dissipate a small fraction of the heat output of the T132.