Greetings,
So I got myself a peculiar VME sparc board, SPARCengine 1e "Polaris". 
This is an early Sparc v7, SPARCstation 1 in VME. It has SunOS 4.1e on it.

I would like to boot it diskless into RTEMS.

Well, the SunOS-provided boot loader chokes on the ELF boot images. It 
can handle only a.out-sunos-big format.
I found a NetBSD boot .net in a.out-sunos-big. The plan is to use it for 
secondary loading of my ELF image.
Boot.net actually starts up on 1e, gives a welcome message (NetBSD sparc 
Secondary Boot revision 1.14), seems to be happy with BOOTP, and asks 
which device to use and which image to load.
After I specify the image it checks BOOTP again, displays one liner:

102800+5212 [22304+19788] = 0x24c44

then displays a few characters of some gibberish and dies. It does not 
look like it downloads the specified image itself, as there is no other 
messages or counters with bytes downloaded (1MB image), and things 
become quiet quickly.

Can anyone make sense of this? Was anyone successful in using NetBSD 
loader on SPARCstation 1? Success stories of loading something to 
SPARCengine 1e?

Many thanks for your insight.
Ivan