It should be pointed out, for the edification of those who are not VLSI people, that transistors with an f_t of 100GHz are not the same thing as transistors fro

It should be pointed out, for the edification of those who are not VLSI people, that transistors with an f_t of 100GHz are not the same thing as transistors from which one can build a credible 100GHz processor. f_t is the input frequency at which the gain through the transistor (biased in the linear region) is unity (1). This has some relation to how fast the transistor can switch from 0 to 1 when biased in the saturation region (the way digital logic works), but it is not 1:1. Likewise, the cycle time of a processor is the delay of the longest path from one flip-flop or latch (storage element) to another flip-flop that is expected to take 1 clock cycle. The length of this path is typically expressed as a multiple of the propagation delay of an inverter driving 4 other inverters (delay grows with output load, or fanout) (FO4 delays http://en.wikipedia.org/wiki/FO4 http://en.wikipedia.org/wiki/FO4). Typically, high-performance processor microarchitectures are designed with a 5 (Pentium IV) - 25 (slower but more power-efficient) FO4 delay critical path. Once you account for clock skew, jitter, process/temperature variation, etc., your processor frequency is 1 to 2 orders of magnitude lower than your transistors' f_t. The authors of this paper are careful to point out that their graphene transistors' f_t is higher than CMOS transistors of the same gate length (240nm), but that is comparing with a ~12-year-old CMOS processes. Modern CMOS processes are faster than this (for instance, this paper http://wwwtw.vub.ac.be/elec/Papers%20on%20web/Papers/DLinten/%5BLinten%5Djournal.pdf http://wwwtw.vub.ac.be/elec/Papers%20on%20web/Papers/DLinten... assumes a 90nm RF CMOS process with an NMOS f_t of 150GHz). Graphene can certainly catch up once they figure out how to shrink the devices, but it will take more than productizing the current state-of-the-art to compete with CMOS.