Dataproducts introduced a very different implementation of the parallel interface for their printers. These connected via the parallel interface allowing applications to be quickly loaded into RAM. EEPROM devices use a serial or parallel interface for data input/output. The serial interface board was $124 and the parallel interface was $119. The 8-bit processor was connected to the 16-bit processor via an internal 32-bit parallel interface. The MSD drives include both an IEEE-488 parallel interface and the custom Commodore serial interface. I/O, which offered a serial and parallel interface, plus a battery-backed clock/calendar. Inexplicably, the drive's ROM contains commands for parallel use, although no parallel interface was available. Initially, the "SCSI Parallel Interface" (SPI) was the only interface using the SCSI protocol.