Automatic drive systems for movable partitions may comprise a floating jamb configured to attach to panels of a movable partition and glide within a pocket. A motor may be configured to extend the movable partition. The motor may be configured for mounting in the pocket on a back side of the floating jamb opposing a front side of the floating jamb to which the panels of the movable partition are configured to attach. An electronics enclosure may be sized and configured to contain electronics to connect to the motor. The electronics enclosure may be configured for positioning in the pocket on the backside in a location offset from the motor. A depth of the electronics enclosure, as measured in a direction in which the floating jamb is mounted to glide, may be less than or equal to a depth of the motor, as measured in the same direction.