This post has been left for historic information. The PET microSD is no longer in production. The replacement SD2PET is available now, more information on the pre-order page.I've been updating the design of the PET microSD, and there are now three different versions to chose from, depending on how you want to connect it, and to what machine. All of these plug into the rear edge connector of a PET from a 2001 up to an 8032 (or variations of the 8032 such as the SuperPET 9000). See later for information on 2001-8 and 8032-SK support.
All the versions of the PET microSD can be used with the original 2001, but 2001's with BASIC 1 need to be upgraded to BASIC 2 or BASIC 4, you can use one of my ROM/RAM boards to have a configurable BASIC 1/2/4 ROM and 8/16 or 32K RAM upgrade.
Which one do you choose? Well choose 1 if you want to move it around between PETs or easily remove it, or don't want to open the PET case. Choose 2 or 3 if you are short of space, or prefer less wires around the back. Choose 2 if you need access to the SD card, Choose 3 if you don't plan to change the card often, or are happy to open the PET as required. Not all PETs support all options, so see the table of which PETs support which boards, which also has buy it now links.