To be honest, I've forgotten many (most) of the details.  But that sounds about right.  As I remember it, it was like SunOS.  The key point was that the kernel only had one view of the memory system period, no FS buffer cache etc...which was a departure from many of the traditional UNIX implementations.    IIRC they did not support BSD's mmap -- but check the SVR3 docs to be sure -- they had the SVR3 user interfaces but none of the BSD ones.  They did support the System V shared memory, however.  I do seem to remember there was something funny in the driver interfaces, it was just like UNIX only different, and that causes some heartache - but it was fairly straightforward to move a DMA driver like getting a VME Xylogics tape controller to work, but it took a little tweaking.  I've forgotten exactly why that was --  it's been a long time ago.

Clem