Before reading David Brownlee's recent suggestion I had attempted to
re-install NetBSD while the RiscPC had the ARM610 processor installed.
Using the Install kernel which Chris Gilbert mentioned here early in February
(3rd?) while copying the contents of BASE.TGZ it stalled twice at 19% - left
for over 15 mninutes with no change - and also dropped to a db> (debug?)
prompt on other occassions.
Suspecting a problem with the CDROM drive I swapped to a different one and
the install still had similar problems so I put my StrongARM processor into
the machine and the Full install ran successfully simply reporting that the
Tests set was unavailable on the CD (version 4.0 ISO from the NetBSD site)
and completing when that set was skipped.
Reverting to the ARM610 processor the system will boot and I can now spend
some time learning with it.
I have a spare ARM610 processor card I will post if someone would like to
make use of it.