The PETdisk is a simple storage device for the Commodore PET series of computers. PETdisk uses a microSD card for mass storage and uses the PET’s IEEE-488 port.

With this solution you can also transfer your PET audio tapes to the SD card, providing, for now, that you invert the waveform in an external audio program.

The IEEE-488 interface has a passthrough, so one can connect a external drive and load or/and transfer programs from unit 8 <-> 9

PETdisk website