This expansion card is an evolution of the Symbiface 3.

Features

Parameters available during the initialization

Activation of a chime at startup: ON/OFF.
Pen sound on touch screen: ON/OFF.
Activation of the integrated 2 MB memory expansion: ON/OFF. Function that can be deactivated if an application or game is not compatible. Or if you want to use another memory extension on an MX4 slot. Warning: do not activate the integrated 2 MB memory extension of the RSF3, at the same time as another external memory extension on an MX4 slot.
464 Memory hack: ON/OFF. If RSF3 is used on a CPC 464, use the patch by @ToTO to take into account the memory extension.
Substitution of ROM 7: ON/OFF Allows you to replace the original Amsdos ROM 7 with another stored on the RSF3. Warning: not compatible with all CPCs. May cause hardware conflict with Z80 data bus.
SE-One: ON/OFF. Allows you to activate the emulation of the MSX SE-One card, which offers an MP3 decoder (with playback of other formats such as AAC, MP4, M4A, WMA, WAV, MID, OGG) + an FM radio.
Symbiface II: ON/OFF. Allows you to activate or not the compatibility mode with the Symbiface II.
Multiplay mouse: ON/OFF. Allows you to enable or disable USB mouse support.
GMT time zone: to set the time offset, based on the time zone.

The RSF3 also contains the following elements:

Emulation of older interfaces like the SSA-1 speech synthesizer, the Amdrum, and the Digiblaster. With programs for each of these interfaces to use them.
Emulation of all the functionalities (SID, MP3, MIDI, FM radio, web radio) of the Amsdap SE-One.
A "System Information" application which summarizes the detailed information of the RSF3 (firmware version, Wifi and network information, activated rombank and list of roms with their positions, the activation status/or not of the M4, the SE -One, CPC 464 hack, Multiplay, SF2, etc.
A drawing application for the stylus.
A “Post-it” application to write whatever you want, like a memory aid.

The 2 MX4 slots are more than sufficient given that with the RSF3 you don't need to have as many as a Mother X4 given that it already includes:

a 2 MB memory extension (can be deactivated if necessary): no need to add another one.
255 rombanks: no need to add a rombank.
M4 Board emulation: no need to add the card of the same name.
Hacker v7.0 in a dedicated rombank: no need to add the card of the same name.
support for a USB mouse: no need to add a Multiplay or an Albireo.
an RTC clock: no need to add a Nova extension or equivalent.
emulation of old audio devices/cards, etc.

The TMTLOGIC team around RSF3 is very active. They regularly offer new features, applications, and firmware updates.

Characteristics, in comparaison with the RSF3: