The SC140, Z180 SBC / Z50Bus Card has been designed primarily to run RomWBW (which includes CP/M):
The recommended version of the RomWBW for this board is
RomWBW sc140
Alternatively, the card can run the Small Computer Monitor.
The recommended version of the Small Computer Monitor for this board is
SCM v1.0 configuration S6.
This configuration of SCM has been written for SC126 but works just as well on SC140.
Small Computer Central 