From ReplayResourcesAvailable from vesalia.de
Network Card for Retro Replay and MMC64
SilverSurfer is an add-on that does NOT fit on MMC Replay and Chameleon. Reports are that a little force will make it fit on the MMC Replay anyhow - your results may vary, but functionality should be given nonetheless. Some sort of extension to the port might solve the situation for the Chameleon.
This high-speed serial connector allows up to (theoretically) 460800 baud with 16 Byte FIFO and a connection to nearly any other computer around. It was originally designed for the Amiga Clockport and utilised for the Retro Replay platform.
Please note that the SilverSurfer can be used with some terminal programs and SuperCPU without Retro Replay mode and achieve very high transfer rates. Someone care to do some testing? :)
The Silversurfer provides full RS232 capabilities and may therefore be used for directly connecting a modem to the port or connect a null-modem cable to another computer.
Interesting application utilising the SilverSurfer can be found under Related Homebrew.