The difference between the equilibrium and switching d/p ratio of a bistable twisted nematic (BTN) liquid crystal display is shown by computer simulation. It is clearly indicated that the optimized d/p ratio has to be determined by the switching rather than equilibrium d/p ratio. It is also shown that the switching d/p ratio is related not only to the pre-tilt angle, but also to liquid crystal viscosities, which indirectly indicates how temperature will affect the BTN device, and that there exists an optimized delay time for the device-driving waveform which will narrow the selection pulse and increase the matrix driving scanning speed. Further, the trade-off between the width of the waveform selection pulse and cell thickness tolerance is considered. By applying the determined optimized conditions and using the multidimensional alignment method, a long-term bistable BTN effect can be demonstrated. (C) 2001 American Institute of Physics.