The difficulties in getting hold of a PETDisk (see below) drove Dave to designing and building a version of his own as described on his blog. Dave generously donated a fully functional board to me that I have used while preparing the feature comparison table below - thanks Dave!.

Whilst a PETDisk "clone" would probably be the lowest cost option for adding an SD based "floppy drive" to a PET, the functionality of the PETDisk firmware is very limited, Steve Gray and Mike Naberezny suggested that Dave have a design that uses the sd2iec firmware used in petSD, petSD+ and petSD-duo, so Dave has developed pet microSD.

This design is a slightly modified version of the original petSD, using a 74LV125A buffer and a filtered 3.3V supply.

Because of the difficulty that hand soldering would present to the average hobbyist, Dave intends to make pet microSD available as a finished product only.

With a view to creating a minimal cost version, but still having better Commodore DOS support than PETDisk, Dave is considering the possibility of enhancing his PETDisk inspired board and developing TS-SD

The duo is basically an advanced and enhanced petSD. A slave MCU (ATmega 328P) is attached to it via I2C and controls the LCD display (192 x 64 pixels) and the rotary encoder. This allows navigation through sub-directories and disk images and present them with a Commodore font with all the special characters found there, 8 lines and sufficient columns.

Nils is currently working on petSD-duo, but the projected price just for the components is becoming a potential issue and there is still quite a bit of work to do before it could be released as a finished article.

I think that it is safe to say that, in the short to medium term, petSD, with some minor revisions, is the best (only?) option.

A photo (from Nils' Flickr page) to show how the finished article may look.

"PETdisk is a simple storage device for the Commodore PET series of computers, using a microSD card for mass storage and uses the PET’s IEEE-488 port." Documentation, schematics, and source code can be downloaded from the PETDisk website that can be used to build your own, the site also has an ordering page where self-assembly kits of ready made units can be purchased.