The feasibility of reversing single bit per particle media at a 1 GHz data rate with a density of 100 Gb/in.(2) is examined. The media particles are cubic with 40 nm side length, 80 nm center to center spacing and perpendicular uniaxial anisotropy. Micromagnetic simulations are employed, and writing of data is done via an elongated probe to provide localized fields at the particle being reversed. The reversal of individual elongated particles is also examined with fields from a moving probe. A 1 GHz data rate appears to be more attainable with cubic particles than with elongated particles. (C) 1999 American Institute of Physics. [S0021-8979(99)71108-4].