I've realized that real NE1000/2000 cards had 2764 as option rom which is 8kB.

I've resized firmware and I barely fit into new constrain.

I use https://www.tindie.com/products/weird/isa-8-bit-ethernet-controller/ as real hardware and it allows 16kB roms which I've initially targeted.

BTW I've added broadcast packet with mac sent when boortom wakes up after geting IP from DHCP server.