Traditional mechanical and analog electronic speed governing systems have served the prime mover market for many years. The absence of certain performance features was accepted in the prevailing economic environment of the equipment. Today, however, this environment is characterized by intense competition and the resultant need for flexibility, reliability and availability at reduced cost. Coupled with product obsolescence, control systems such as speed governing and load sharing are increasingly the subject of retrofit interest.This paper presents results of a study to optimize the performance of digital speed governing retrofits applied to medium-speed, large bore diesel generators. These results are also considered applicable to diesel generators of other operating speeds and sizes. Investigation included the influence of certain operating variables on governor performance such as load stability during parallel operation and frequency stability and transient response during isolated operation. The effect of each variable on overall performance is quantified and provides useful guidance for digital governing retrofits. The inherent advantages of digital technology can be fully exploited by this type of parametric investigation and guideline development.