Electric machine drive systems, and related electric machine embodiments, include technologies for providing redundancy of shaft information of one or more electric machines between converter controllers of the corresponding system. The converter controllers are configured to control operation of power converters, which control one or more electric machines. The disclosed technologies include establishing one or more communication buses between the converter controllers to share the shaft information, which may be based on analog signals from a single, common resolver and/or from different, redundant resolvers depending on the embodiment. For example, in some embodiments, converter controllers communicatively connected to the same resolver may include separate resolver-to-digital converters (RDCs) to provide redundancy of the RDCs.