There is even more room at the top. The physical limits are as follows. A computer "with a mass of one kilogram confined to a volume of a liter" can perform at most 2:71 * 10^50 operations per second on 2.13*10^31 bits. See:

Lloyd, S. Ultimate physical limits to computation. Nature volume 406, 1047–1054 (2000)

Bremermann, H. J. Minimum energy requirements of information transfer and computing. Int. J. Theor. Phys. 21, 203–217 (1982)

Bekenstein, J. D. Energy cost of information transfer. Phys. Rev. Lett. 46, 623–626 (1981)