To prevent lag in computronium caused by upload overpopulation in an ISO, some few ISOs have taken to 'Derridaism', which is Named after the Old Earth French late Industrial Age philosopher Jacques Derrida. The basic concept is to take the population's personality types and break them down into their smallest cogent fractions - e.g., a love for baseball, a memory of breeze in your hair, etc. These fractions are then assigned a weight depending on how common they are across the population's experience base.
The ISO saves a large amount of processing power and the population's experiences are maintained, at the (they consider) small cost of individual personalities.
There are also semi-Derrida ISOs, which allow the creation of a meta-personality by individual personalities merging into the core meta-personality via the above method. There are even a few quasi-Derrida ISOs which allow both merging and separation from the core meta-personality, but these are quite rare. (who wants to loose a portion of their personality? And the meta-personality quickly tends to gain control of the ISO...)