Sorry for talking about non-NetBSD, but I hope this may be of some 
help...
On my MacOS X machine, binutils and gcc for mips64 could be built 
without any effort. Like:

% cd binutils-2.15
% ./configure --prefix=/usr/local/mips64-elf 
--program-prefix=mips64-elf- --target=mips64-elf
% make
% sudo make install
% cd ../gcc-3.4.2
% mkdir build
% cd build
% ../configure --prefix=/usr/local/mips64-elf 
--program-prefix=mips64-elf- --target=mips64-elf
% make CC='cc -no-cpp-precomp' CFLAGS="-O2 -fomit-frame-pointer"
% sudo make install

Now, what seems like to be the toolchain is in 
/usr/local/mips64-elf/bin... though I've not tested at all. I'm sorry 
if I was speaking something out of the point.

On 2004/07/16, at 19:59, Richard Braun wrote:

> Hi,
>
> I have an Octane IP30 system, which seems to be able to load only
> ELF 64 bits executables. Is the toolchain able to build such 
> executables
> (I guess not), and what should be done to make such a toolchain ?
>
> -- 
> Richard Braun