Supply units having an associated electronically-readable memory device

A machine, such as a phase change or solid ink printing apparatus, has at least one multiple supply unit in the form of an ink stick disposed therein. The ink stick has an electronically-readable memory device associated therewith, and the memory device has stored therein electronic data related to the ink stick and readable by the machine. The memory device is attached to the ink stick and removed before the ink stick is used for printing in the machine. In another aspect, the memory device is attached to a container for the ink stick. The container is a cartridge for use in the machine, or a container for packaging the ink stick. The machine may include a coupler configured to read electronic data from the memory device while the memory device is positioned external to the printing apparatus, thus allowing the machine to verify the suitability of the ink stick before it is installed in the machine.