VA0 vs VA1
VA0 vs VA1
The single most important hardware detail for Dreamcast modding is your mainboard revision. Sega produced two principal versions, and the difference shapes which mods you can install and how well they work.
How to tell them apart
Open the console and look for a silkscreen marking on the mainboard reading VA0 or VA1. The revision is printed directly on the board, so once you are inside it is unmistakable.
VA1
The VA1 revision is the most common and the most modding-friendly. It generally reads burned CD-R media most reliably, and it is the board that GDEMU is specifically designed around. If you have a VA1, you have the widest range of options.
VA0
The earlier VA0 revision works well too, but it differs in connector layout and sometimes in how it handles burned discs. GDEMU is not the natural fit here; instead, USB-GDROM and the Terraonion MODE both support VA0 and are the recommended ODEs for it.
Why it matters
Buying an ODE without checking your revision is the most common mistake newcomers make. A GDEMU intended for VA1 will not drop neatly into a VA0. Confirm the marking first, every time.
Once you know your revision, the ODE comparison page will point you to the right hardware.