Difference between sun4, sun4c and sun4m subarchitectures

[Michael Sokolov]

Hello ClassicCmpers,

Does anyone know what are the real technical differences between sun4,
sun4c and sun4m subarchitectures of SPARC from the viewpoint of an OS
kernel writer?  I know that SunOS treats them as different kernel
architectures while Net/OpenBSD has a unified SPARC kernel, as does
Linux if I'm not mistaken.  I'm trying to evaluate the pros and cons
of the two approaches.  Reason: a friend of mine is porting 4.3BSD-Quasijarus
to SPARC and I'm trying to help him with the key architectural decisions.
We have the SunOS 4.1.4 source.

MS