I have just got RISC OS 4.27 working on my Kinetic RiscPC and
am pleased to report that NetBSD still boots successfully with
this version of RISC OS using the old bootloader. There are two
caveats, though:

1) If you have two SIMM strips in your RiscPC in addition to the
   Kinetic card, you will have to take one of them out. This is
   because of the memory organisation under RISC OS 4.27. With
   two SIMM strips, RISC OS now has five physical memory areas.
   This is one too many for the bootloader and, more importantly,
   for the NetNSD kernel. The problem is that the kernel is passed
   a fixed sized table (four entries) by the bootloader for the
   physical memory layout. There are now five entries in the table
   so things don't quite work... NetBSD still boots but I found
   that the screen was messed up. Everything is okay if you take
   out one of the SIMM strips. (Actually, the physical memory is
   different again: there are only *three* areas listed...)

2) Not so important this one. When you reboot RISC OS, RISC OS
   moans that the machine was not shut down cleanly.

Apart from that, my quick test of NetBSD did not reveal any
problems.

Dave Daniels