In computer magnetic tape systems, a primary factor in character rate is recording density. Pulse time displacement places a direct limit on the maximum bit density which may be used in parallel NRZI recording systems in which recovery of the information on readback depends on correct synchronism of all tracks. Measurement techniques for evaluation and analysis of pulse time displacement are described. A sawtooth oscilloscope display is particularly useful for observing time displacement as a function of time. The various components of time displacement and their causes, such as skew and pulse crowding, and methods used to reduce them are discussed. This study led to the adoption of a recording density exceeding 500 bits per inch for the IBM 729-III Magnetic Tape Unit.