Running latest qemu from git https://github.com/qemu/qemu 

./qemu-system-hppa --version
QEMU emulator version 4.0.50 (v4.0.0-270-ga6ae23831b-dirty)
Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers

netbsd.img is a 8GB file created via the following 

$ dd if=/dev/zero of=netbsd.img bs=1024 count=8M

# ./qemu-system-hppa -boot c -serial telnet::4441,server -drive if=scsi,bus=0,index=6,file=./netbsd.img,format=raw \
 -serial mon:stdio -D /tmp/foo -nographic -m 512 -d nochain -cdrom ./NetBSD-8.99.37-hppa.iso -D /tmp/foo  -net nic -net tap