Adding a little padding to the output of elf2ecoff works just fine.  I
guess the PROMs really were reading either pagesized blocks or 1K
buffers, were trying to read past the end of the file, and weren't
handling the resulting TFTP error gracefully.

I've committed the a fix that does that, the ECOFF symbol tables will
have to wait a while.

A kernel built with today's elf2ecoff works fine on my 5000/150.  I've
put the binary on ftp.netbsd.org.  If someone (Tohru Nisimura or
Gregory McGarry or anyone else) could try running elf2ecoff on an ELF
kernel, TFTPbooting the resulting ECOFF kernel, please let me know if
it works.  I'm pretty sure it will, and if it does, there are no known
restrictions on TFTP-booting ioasic machines.

Could someone (Simon Burge, maybe) try a 5000/240 and 5000/260?

Thanks
--Jonathan