Trick I've used since the 90's with the PAR 4m+: internal storage stays until power is lost, so I don't even bother with the battery anymore. Instead, I got in the habit of, when I'm done playing, hitting the reset button on the console to go back to the memory management screen, and manually copying the internal storage over to the cart. Kinda like holding reset when turning off zelda on the NES, but a little more involved. There is, the DC's modem port, called the G2 port, is actually essentially a PCI port. The main thing holding it back is that the specific model of the SH4 in the dreamcast, the SH7751 in the dreamcast lacks a PCI controller. The SH4 added a PCI controller in a later revision (SH7751R). That said, you can put a raspberry pi between your device and the port to act as a controller and it'll work fine. There have been lots of things unofficially connected to the Dreamcast this way. A smarter, easier, much cheaper way to interface with the dreamcast is through the serial port, however. A $5 FTDI 232 serial to USB converter will let you do all sorts of things with the Dreamcast.
Friendly reminder that, whenever you notice that an auction with some super rare stuff is happening/going to happen, you directly tell a preservation group instead of publicly posting/tweeting about it. Else, you're just making things more difficult to preserve. Yes, even when the info is public.
