thanks Todd.  Actually i just read from Freebsd-maillist below
that Freebsd's DOS netboot.com-v1.4  will probably not work with
diskless NetBSD kernel.
But i was wondering if it would be so hard to modify netboot.com
to work with NetBSD.  I guess it would take porting some code
from the NetBSD1.1 PROM boot program in i386/netboot into the
FreeBSD2.1 DOS or PROM code in i386/boot/netboot to get the
kernel interactions correct.  Are there some experts out there
who can help me with this or let me know if i'm on the right track.
(Hopefully the NetBSD PROM boot code is not out of date with
the NetBSD 1.1 or later diskless kernels.) One advantage of using
FreeBSD's DOS netboot.com is that NE2000 cards are supported.

From: hackers@freebsd.org
>> Can someone who does diskless booting under FreeBSD please
>> review this diskless(8) man page obtained from NetBSD and
>> see if it reflects reality, and possibly even add some FreeBSD
>> specific info to the man page where appropriate?  Thanks.
>This is one of the divergent areas in the two systems, unfortunately,
>but since I've been playing with NFS diskless on both *BSD systems
>I'll write it up.
>There are minor differences in the names of files etc that tftp looks
>for, and some more major differences in the interaction between the
>boot code and the kernel.

From: Todd T. Fries
:: ok, i have found the DISKLESS kernel config file in the conf directory, 
and
:: it configures the root to go over nfs.
:: Has anyone tried using the FreeBSD Netboot.com DOS program to Diskless 
boot
:: the NetBSD kernel?  I will be trying this from an AIX 3.2 BOOTP and TFTP
::server. Will it work?
:I have used the program on an ethernet that has bootp servers, and have
:hard-coded it to work with a particular tftp server...
:My point in telling you this is that the tftp part of AIX I know from this
:experience works.