Modern mass storage solution for Commodore PETs

Table of contents

petSD front view

The first petSD, 2011

The hardware-design is obsolete and is going to get replaced by a couple of other devices. The software though still supports the old petSD and will do so in the future.

If you're looking for a networking-device, please have a look at the Flyer Internet Modem. Though the networking hardware of the old petSD has proven to work, there never was any support by software and it's highly unlikely that there will ever be one.


The hardware's heart is an Atmel ATmega 1284P microcontroller with 128 KB flash memory and 16 KB RAM, running at 18.432 MHz. His peripherals are:

  • IEEE-488 interface with bus drivers (75160/ 75161)
  • SD card slot
  • USB interface via virtual serial port (FT232RL)
  • real time clock with battery backup (DS1307)
  • 10 MBit Ethernet interface (ENC28J60)
  • I²C-Bus to connect hardware expansions
  • two keys, red and green LEDs
  • 6 pin ISP connector

Two firmwares are available:


NODISKEMU is a fork of sd2iec by Ingo Korb (et al.).

It supports SD-, SDHC- and MMC cards formatted with FAT 12/16/32 and the real time clock.

Files can reside in directories of the FAT tree as well as inside disk images like D64, D80, D82 and others. The real time clock can be read and set via the command/status channel and is used to set time stamps for files.

USB gives you only some debug messages, Ethernet isn't supported at all.

NODISKEMU is free software, GPL2 only.

Firmware XD2031

XD2031 by André Fachat (et al.) requires a host computer (connected via USB) and supports multiple drives at the same time assignable to:

  • a directory of the host computer
  • a file server (FTP) accessed by the host
  • a web server (HTTP) accessed by the host

It has very stable IEEE-488-routines and is designed to be expandable by further endpoints, so we may see a standalone version in the future.

XD2031 is free software, GPL2 or later.



Distribution has been discontinued. The assembly instructions are still available via

Many thanks to Roland "Donald" Hager for the distribution.