Nvidia announced the GeForce 800M top to bottom line-up of new notebook GPUs. They deliver the usually double digit jumps in performance of 30%, 40% and in some cases even 60% year on year. And we ha... GeForce 800M series of notebook GPUs Have Launched
nV could have dealt serious blow to AMD, but instead they took 780M, boosted its clocks by 110MHz and named it 880M. GTX870M situation is: GTX 680M got renamed to 775M and now to 870M (at least it got 220MHz boost now, as 775M had same as 680M).
So M880 and M870 are rebrand, leaving only lower end M860 / M850 with Maxwell. I hope 880 won't be re-branded 780 for desktop.