I have a test kernel available if anyone wants to give it a shot.  You 
can find it at http://www.roadsign.com/~gillham/xbox/ along with a 
2.41-dev Cromwell BIOS, XBE, and etherboot chainload image.

If you have Cromwell 2.40 in flash already you can chainload the 
ethboot.bin file via tftp and then the ethboot.bin will be able to load 
a NetBSD kernel.  Cromwell 2.40 is NOT able to correctly load a NetBSD 
kernel, you have to have 2.41-dev. (aka Cromwell CVS)

I have the cromwell.bin (256k image) flashed on my modchip and it is 
working well.  If you chain load 2.41 from 2.40 you will probably have 
to do a filename swap after booting 2.41 and before booting the kernel.  
(e.g. if you are passing the dhcp filename of 'boot.xbox' you need to 
first point it to ethboot.bin and then to netbsd after loading the 2.41 
ethboot and before selecting etherboot again)

I have NOT tested the xromwell.xbe image, but in theory something like 
EvoX can load it and then you can netboot the kernel.  This is just the 
binary built along with the cromwell.bin and ethboot files (which both 
work for me), so I am guessing it will work.

The console attaches late, about 20-30 seconds after the kernel loads.  
So you'll just have a static Cromwell BIOS screen for a bit. The led 
will be flash red briefly and go back to green when the kernel is 
starting.  The nfe(4) driver is not working properly (watchdog timeout 
issues) so it is not enabled and you'll need a usb ethernet plugged in 
via an adapter cable or a case mod if you want to have networking at the 
moment.

I've found that the Cromwell BIOS doesn't deal well with my usb keyboard 
plugged in during boot, so I wait until the kernel is up before plugging 
it in.

Anyway, it is super late and I need to get some sleep.  I can post more 
later today if there is any interest.

Oh, one other thing, if you have the X3LCD (works with X3 chip) you 
should see "NetBSD/i386" on the LCD.  The process of writing to the lcd 
is pretty basic, so I am guessing it shouldn't be a big deal if you 
don't have it.

-Andrew