There are rumours of cheap Chinese SD cards that don’t follow the official spec and allow you to change to them – I now have large pile of cheap Chinese SD cards on my desk, but unfortunately none of them did allow it. For example, if you want to change the supposedly read-only ID on various kinds of RFID tag you can simply buy a special version from China that allows it (often referred to as gold or magic cards). There is surprisingly little info out there about this, when it’s easy for other devices. I’ve spent a while trying to work out how to change the ID on some cards. This can result in you being stuck with a smaller card than you’d like in a device or not being able to use a backup in case of damage.
The CID register on SD cards is supposed to be read-only, which means it can be used to lock devices to specific SD cards, preventing the user swapping them out, which is very annoying.
