In message <20040324051226.GB23417@seekingfire.com>, you write: 

-> 1. I'm unable to boot any kernel from releng.netbsd.org newer than the
-> 20040103 build. They all boot, to an extent, but freeze at this point: 
-> 
-> (snip)
-> root file system type: ffs
-> Tue Mar 23 22:59

ENOCLUE here.  My O2 hasn't been on in entirely too long...

-> 2. While 'hinv' shows more than 256MiB of RAM, the NetBSD kernel doesn't
-> appear to recognize it. I've tried more recent kernels from
-> releng.netbsd.org (since the memory count is displayed before they
-> freeze, which is handy) and the situation remains right up to the newest
-> kernels I can try.

The O2 code relies on ARCS to give us the memory map; this is a limitation
of ARCS, which will only report up to 256MB in the memory map it passes to
us.  Additionally, to use large(r) amounts of memory, the kernel might have
to resort to mapping memory via KSEG2, which I don't think we currently 
support.  I don't remember the O2 memory map off the top of my head, but
I think we definitely can't support more than 320MB without KSEG2 mapping
and it may actually be only 256MB.

The same is true of the IP22/IP24 machines (actually, there the hardware
memory map imposes additional restrictions because there's a hole in the
memory map between 0 and 128MB).

See the thread recently about 256+ MB on port-mips as well.

--rafal

----
Rafal Boni                                                     rafal@pobox.com
  We are all worms.  But I do believe I am a glowworm.  -- Winston Churchill