I have an X-Mass on slot 2 of the MX4 Board.
Behind, the M4. No other extensions.
Here's what I get at power ON:
(http://orgams.wikidot.com/local--files/features/m4_xmass_boot_fail.jpg)
The CPC is perfectly operating, as the commands show.
I deactivated the ROMs for the picture.
All the zero-initialised RAM is corrupted like that (e.g. ?peek(&4000) = 189)
I had the same behaviour on another CPC 6128, and my ports are clean!
No problem afterwards (with CPC hard reset or M4 reset).
So, not dramatic (at least I hope!).
What firmware version is the M4 board using?
Other than that I have no experince with the X-Mass board, maybe others have tried it along with M4 board?
M4 and xMass with iMPdos work perfectly together....
You can also do some copies between these two fabulous cards.
M4rom is installed on slot 6 (on m4 board)
IMPdos is installed on slot 3 (on xmem board)
@Duke (https://www.cpcwiki.eu/forum/index.php?action=profile;u=1624) I'm using the version 2.0.5, I think it's the latest.
@Ast (https://www.cpcwiki.eu/forum/index.php?action=profile;u=573) Good to know, but that's not a DOS issue here. Both cards works, I'm just a bit wary about hardware interferences.