The N0 stepping. Yep.

I think the last mainstream Intel CPUs that lacked their EM64T tech (at the time), was the Intel Core. As of the core 2, all mainline chip series came with 64bit by default, including all of the core i* series.

Prior to core i* you had to almost be careful when buying a CPU so you could make sure you get 64bit, if you wanted the feature, but after that point, everything had it, so it didn’t matter.

I don’t think anyone in their right mind is still using a computer that’s older than a core 2 at this point.