The Sutcliffe Electronics Internal Cartridge Port Expander
Inside one of my Dragon 64s acquired a few years ago was a small, seemingly quite insignificant board. Internally connected was a bare DragonDOS interface board with a 34-way floppy drive cable exiting the rear of the Dragon through a neatly carved gap. This little board was a cartridge port expander, designed to provide an additional expansion port inside the Dragon, whilst retaining the external through-port.
I confess I didn’t attach much significance to this little board to start with, but as I began to experiment with other projects – like the WordPak 2+ board, it’s usefulness came to light as a way to have both a DOS solution and an additional add-on board connected.
I’d been experimenting with the Premier Sprite boards that David Linsley had loaned me at the 2019 Dragon Meetup in Cambridge, and had first tried to make use of this expander with the Sprite. It didn’t work when a DragonDOS or compatible cartridge was inserted because the Sprite board contained an onboard ROM and thus made use of the P2 line – essentially there was a conflict between the DragonDOS ROM and the Sprite ROM.
So the little expander board languished in a cupboard a while longer until I decided to buy one of the WordPak 2+ boards and experiment with it.
Because the WordPak 2+ board has no ROM, when combined with a CocoSDC, DragonMMC or DragonDrive using the Sutcliffe Electronics board expander, everything works just fine. So I was finally able to concentrate on having a disk system of some sort connected to the computer at the same time as some serious hardware upgrades.
So effective was the board expander that I decided I should make and offer replica versions to the Dragon community. Richard Sutcliffe, creator of the original board expander was happy for me to do so, and also told me a few details about the original board. Richard still runs Sutcliffe Electronics, though now concentrates mainly on security systems.
The main differences between my replica and the original are the build, as electronically the device is identical. My device is very much more ‘board only’, with the onus on the end-user to customise the fitting aspects, ensuring stability and durability, whereas the original boards were fitted with moulded plastic which was then mounted using screws, onto the lower part of the Dragon’s case. The other main difference is that my boards are supplied with a header and jumper, so that the original switch becomes optional.