What is the purpose for "none" machine?

[Matwey V. Kornilov]

Hello,

I am playing with qemu-system-avr currently.
I see that there is an "empty machine" called "none" in

    qemu-system-avr -M help

list.

Is it a real thing? I am failed to run any code with "none" machine.
For instance,

    qemu-system-avr -M 2009 --cpu avr5-avr-cpu -bios ~/temp/a168.elf -S 
-s --nographic

works, while

    qemu-system-avr -M none --cpu avr5-avr-cpu -bios ~/temp/a168.elf -S 
-s --nographic

just increments PC until reach the end of memory:

    qemu-system-avr: execution left flash memory
    Aborted (core dumped)

Thanks.