This instructable author did some experimental trial & error development in order to produce his own additional game/memory cards for the Hydra console –
You will need more serial flash chips. Although 24LC256 and 24LC1024 are mentioned by the author of the Hydra manual, I’ve used 24LC512, which has 64K of bytes on it. Almost all of the hydra software I’ve seen runs in 32K, and therefore which ever chip is most readily available or cheapest is recommended. Also recommended is getting DIP chips instead of surface mount if it’s available, even if they cost a little bit more.
You can obviously use up your experimenter’s card to make another game card, but I saved mine. You can easily etch a single sided board or not even etch it. I had a stale bottle of ammonium persulfate that did not etch, so I cut away the excess copper with a dremel tool after etch failure.
(Note to self: Ferric Chloride etchant has a much longer shelf life.)
The boards can be single sided because all of the pins used for memory are on the back side of the board.
This is just about as ‘DIY’ as game development gets – (that being said, someone will now show up rolling their own resistors for game hardware dev) – How to Make more game memory / cards for the Hydra Game Console
In the Maker store:
HYDRA Game Console