Cortical neurons group into minicolumns of perhaps a hundred neurons and macrocolumns of a few hundred minicolumns, with perhaps 1,000 macrocolumns to a cortical map. Our best guess for the timescale is that our final-stage AI will reach transhumanity sometime between 2005 and 2020, probably around 2008 or 2010. As always with basic research, this is only a guess, and heavily contingent on funding levels. The impact of even a single transhuman AI would be tremendous. The basic dynamic of the Singularity is positive feedback - smarter minds are better at inventing even smarter minds.
Intelligence creates technology which enhances intelligence.
While the process of self-enhancement must eventually reach a limit for any given piece of hardware, this bottleneck only exists until the transhuman AI can assist in the development of new hardware. Or produce any other one-kilogram object, from diamond to hamburger, given a complete specification and a feedstock containing the needed atoms. This is more than enough to run an AI, even a transhuman AI, at a millionfold or greater subjective speedup. Nanotechnology is a field that has matured considerably in the past decade. Companies such as Zyvex are pioneering the automation of what tools exist.